diff --git a/.formatter.exs b/.formatter.exs
index 071db7ed..613206eb 100644
--- a/.formatter.exs
+++ b/.formatter.exs
@@ -24,6 +24,8 @@ spark_locals_without_parens = [
   authorize_if: 2,
   authorize_unless: 1,
   authorize_unless: 2,
+  avg: 3,
+  avg: 4,
   base_filter: 1,
   before_action?: 1,
   belongs_to: 2,
@@ -50,6 +52,7 @@ spark_locals_without_parens = [
   create_timestamp: 2,
   custom: 2,
   custom: 3,
+  custom: 4,
   debug: 1,
   debug: 2,
   default: 1,
@@ -97,6 +100,7 @@ spark_locals_without_parens = [
   has_one: 3,
   identity: 2,
   identity: 3,
+  implementation: 1,
   input: 1,
   integer_primary_key: 1,
   integer_primary_key: 2,
@@ -113,10 +117,14 @@ spark_locals_without_parens = [
   map: 2,
   map: 3,
   match_other_defaults?: 1,
+  max: 3,
+  max: 4,
   max_page_size: 1,
   message: 1,
   metadata: 2,
   metadata: 3,
+  min: 3,
+  min: 4,
   modify_query: 1,
   module: 1,
   name: 1,
diff --git a/lib/ash/actions/sort.ex b/lib/ash/actions/sort.ex
index 44c1ce87..39b8de44 100644
--- a/lib/ash/actions/sort.ex
+++ b/lib/ash/actions/sort.ex
@@ -164,6 +164,9 @@ defmodule Ash.Actions.Sort do
 
           {field, {:ok, aggregate.type}}
 
+        %{name: name, kind: :custom, type: type} ->
+          {name, type}
+
         %Ash.Resource.Aggregate{} = agg ->
           attribute_type =
             if agg.field do
diff --git a/lib/ash/api/info/diagram.ex b/lib/ash/api/info/diagram.ex
index 5266967b..aa733c98 100644
--- a/lib/ash/api/info/diagram.ex
+++ b/lib/ash/api/info/diagram.ex
@@ -43,6 +43,10 @@ defmodule Ash.Api.Info.Diagram do
     |> Enum.sort()
   end
 
+  defp aggregate_type(_resource, %{kind: :custom, type: type}) do
+    short_type(type)
+  end
+
   defp aggregate_type(resource, aggregate) do
     attribute_type =
       if aggregate.field do
diff --git a/lib/ash/filter/filter.ex b/lib/ash/filter/filter.ex
index db2303ca..f975292c 100644
--- a/lib/ash/filter/filter.ex
+++ b/lib/ash/filter/filter.ex
@@ -2213,7 +2213,10 @@ defmodule Ash.Filter do
                  aggregate_query,
                  aggregate.field,
                  aggregate.default,
-                 aggregate.filterable?
+                 aggregate.filterable?,
+                 aggregate.type,
+                 aggregate.constraints,
+                 aggregate.implementation
                ) do
           case parse_predicates(nested_statement, query_aggregate, context) do
             {:ok, nested_statement} ->
@@ -2704,7 +2707,10 @@ defmodule Ash.Filter do
                      aggregate_query,
                      aggregate.field,
                      aggregate.default,
-                     aggregate.filterable?
+                     aggregate.filterable?,
+                     aggregate.type,
+                     aggregate.constraints,
+                     aggregate.implementation
                    ) do
               {:ok, %{ref | attribute: query_aggregate, resource: related}}
             else
diff --git a/lib/ash/query/aggregate.ex b/lib/ash/query/aggregate.ex
index 22fcc209..1a05bf41 100644
--- a/lib/ash/query/aggregate.ex
+++ b/lib/ash/query/aggregate.ex
@@ -9,6 +9,8 @@ defmodule Ash.Query.Aggregate do
     :field,
     :kind,
     :type,
+    :constraints,
+    :implementation,
     :authorization_filter,
     :load,
     filterable?: true
@@ -16,7 +18,7 @@ defmodule Ash.Query.Aggregate do
 
   @type t :: %__MODULE__{}
 
-  @kinds [:count, :first, :sum, :list]
+  @kinds [:count, :first, :sum, :list, :max, :min, :avg, :sum, :custom]
   @type kind :: unquote(Enum.reduce(@kinds, &{:|, [], [&1, &2]}))
 
   alias Ash.Actions.Load
@@ -28,7 +30,27 @@ defmodule Ash.Query.Aggregate do
   @doc false
   def kinds, do: @kinds
 
-  def new(resource, name, kind, relationship, query, field, default \\ nil, filterable? \\ true) do
+  def new(
+        resource,
+        name,
+        kind,
+        relationship,
+        query,
+        field,
+        default \\ nil,
+        filterable? \\ true,
+        type \\ nil,
+        constraints \\ [],
+        implementation \\ nil
+      ) do
+    if kind == :custom && !type do
+      raise ArgumentError, "Must supply type when building a `custom` aggregate"
+    end
+
+    if kind == :custom && !implementation do
+      raise ArgumentError, "Must supply implementation when building a `custom` aggregate"
+    end
+
     attribute_type =
       if field do
         related = Ash.Resource.Info.related(resource, relationship)
@@ -36,14 +58,16 @@ defmodule Ash.Query.Aggregate do
       end
 
     with :ok <- validate_path(resource, List.wrap(relationship)),
-         {:ok, type} <- kind_to_type(kind, attribute_type),
+         {:ok, type} <- get_type(kind, type, attribute_type),
          {:ok, query} <- validate_query(query) do
       {:ok,
        %__MODULE__{
          name: name,
          resource: resource,
+         constraints: constraints,
          default_value: default || default_value(kind),
          relationship_path: List.wrap(relationship),
+         implementation: implementation,
          field: field,
          kind: kind,
          type: type,
@@ -53,6 +77,12 @@ defmodule Ash.Query.Aggregate do
     end
   end
 
+  defp get_type(:custom, type, _), do: {:ok, type}
+
+  defp get_type(kind, _, attribute_type) do
+    kind_to_type(kind, attribute_type)
+  end
+
   defp validate_path(_, []), do: :ok
 
   defp validate_path(resource, [relationship | rest]) do
@@ -93,7 +123,11 @@ defmodule Ash.Query.Aggregate do
   def default_value(:count), do: 0
   def default_value(:first), do: nil
   def default_value(:sum), do: nil
+  def default_value(:max), do: nil
+  def default_value(:min), do: nil
+  def default_value(:avg), do: nil
   def default_value(:list), do: []
+  def default_value(:custom), do: nil
 
   defp validate_query(nil), do: {:ok, nil}
 
@@ -114,9 +148,14 @@ defmodule Ash.Query.Aggregate do
   end
 
   @doc false
+  def kind_to_type({:custom, type}, _attribute_type), do: {:ok, type}
   def kind_to_type(:count, _attribute_type), do: {:ok, Ash.Type.Integer}
   def kind_to_type(kind, nil), do: {:error, "Must provide field type for #{kind}"}
-  def kind_to_type(kind, attribute_type) when kind in [:first, :sum], do: {:ok, attribute_type}
+  def kind_to_type(:avg, _attribute_type), do: {:ok, :float}
+
+  def kind_to_type(kind, attribute_type) when kind in [:first, :sum, :max, :min],
+    do: {:ok, attribute_type}
+
   def kind_to_type(:list, attribute_type), do: {:ok, {:array, attribute_type}}
   def kind_to_type(kind, _attribute_type), do: {:error, "Invalid aggregate kind: #{kind}"}
 
diff --git a/lib/ash/query/query.ex b/lib/ash/query/query.ex
index 2da038ea..e9215966 100644
--- a/lib/ash/query/query.ex
+++ b/lib/ash/query/query.ex
@@ -929,7 +929,10 @@ defmodule Ash.Query do
                  aggregate_query,
                  aggregate.field,
                  aggregate.default,
-                 aggregate.filterable?
+                 aggregate.filterable?,
+                 aggregate.type,
+                 aggregate.constraints,
+                 aggregate.implementation
                ) do
           query_aggregate = %{query_aggregate | load: field}
           new_aggregates = Map.put(query.aggregates, aggregate.name, query_aggregate)
@@ -1418,18 +1421,21 @@ defmodule Ash.Query do
   def aggregate(
         query,
         name,
-        type,
+        kind,
         relationship,
         agg_query \\ nil,
         default \\ nil,
-        filterable? \\ true
+        filterable? \\ true,
+        type \\ nil,
+        constraints \\ [],
+        implementation \\ nil
       ) do
     {field, agg_query} = Keyword.pop(agg_query || [], :field)
 
     query = to_query(query)
     relationship = List.wrap(relationship)
 
-    if Ash.DataLayer.data_layer_can?(query.resource, {:aggregate, type}) do
+    if Ash.DataLayer.data_layer_can?(query.resource, {:aggregate, kind}) do
       agg_query =
         case agg_query do
           [] ->
@@ -1442,12 +1448,15 @@ defmodule Ash.Query do
       case Aggregate.new(
              query.resource,
              name,
-             type,
+             kind,
              relationship,
              agg_query,
              field,
              default,
-             filterable?
+             filterable?,
+             type,
+             constraints,
+             implementation
            ) do
         {:ok, aggregate} ->
           new_aggregates = Map.put(query.aggregates, aggregate.name, aggregate)
@@ -1461,7 +1470,7 @@ defmodule Ash.Query do
       add_error(
         query,
         :aggregate,
-        AggregatesNotSupported.exception(resource: query.resource, feature: "using")
+        AggregatesNotSupported.exception(resource: query.resource, feature: "using #{kind}")
       )
     end
   end
diff --git a/lib/ash/resource/aggregate.ex b/lib/ash/resource/aggregate/aggregate.ex
similarity index 89%
rename from lib/ash/resource/aggregate.ex
rename to lib/ash/resource/aggregate/aggregate.ex
index 669b0c46..b51ea8a1 100644
--- a/lib/ash/resource/aggregate.ex
+++ b/lib/ash/resource/aggregate/aggregate.ex
@@ -5,6 +5,9 @@ defmodule Ash.Resource.Aggregate do
     :relationship_path,
     :filter,
     :kind,
+    :implementation,
+    :constraints,
+    :type,
     :description,
     :private?,
     :field,
@@ -27,7 +30,12 @@ defmodule Ash.Resource.Aggregate do
       links: []
     ],
     kind: [
-      type: {:in, [:count, :first, :sum, :list]},
+      type:
+        {:or,
+         [
+           {:in, [:count, :first, :sum, :list, :avg, :max, :min, :custom]},
+           {:tuple, [{:in, [:custom]}, Ash.OptionsHelpers.ash_type()]}
+         ]},
       doc: "The kind of the aggregate",
       required: true,
       links: []
@@ -81,7 +89,7 @@ defmodule Ash.Resource.Aggregate do
           relationship_path: list(atom()),
           filter: Keyword.t(),
           field: atom,
-          kind: :count | :first | :sum | :list,
+          kind: Ash.Query.Aggregate.kind(),
           description: String.t() | nil,
           private?: boolean,
           default: term
diff --git a/lib/ash/resource/aggregate/custom_aggregate.ex b/lib/ash/resource/aggregate/custom_aggregate.ex
new file mode 100644
index 00000000..12cdec93
--- /dev/null
+++ b/lib/ash/resource/aggregate/custom_aggregate.ex
@@ -0,0 +1,21 @@
+defmodule Ash.Resource.Aggregate.CustomAggregate do
+  @moduledoc """
+  The root behavior for a custom aggregate.
+
+  See data layers for their implementation of custom aggregates.
+  """
+  @type t :: {module(), Keyword.t()}
+  @callback describe(t()) :: String.t()
+
+  defmacro __using__(_) do
+    quote do
+      @behaviour Ash.Resource.Aggregate.CustomAggregate
+
+      def describe({module, opts}) do
+        inspect({module, opts})
+      end
+
+      defoverridable describe: 1
+    end
+  end
+end
diff --git a/lib/ash/resource/dsl.ex b/lib/ash/resource/dsl.ex
index ba6aac9a..8a7c70e1 100644
--- a/lib/ash/resource/dsl.ex
+++ b/lib/ash/resource/dsl.ex
@@ -956,6 +956,56 @@ defmodule Ash.Resource.Dsl do
     auto_set_fields: [kind: :first]
   }
 
+  @max %Spark.Dsl.Entity{
+    name: :max,
+    links: [
+      guides: [
+        "ash:guide:Aggregates"
+      ]
+    ],
+    describe: """
+    Declares a named `max` aggregate on the resource
+
+    Supports `filter`, but not `sort` (because that wouldn't affect the max)
+    """,
+    examples: [
+      """
+      max :first_assigned_ticket_subject, :assigned_tickets, :severity do
+        filter [active: true]
+      end
+      """
+    ],
+    target: Ash.Resource.Aggregate,
+    args: [:name, :relationship_path, :field],
+    schema: Ash.Resource.Aggregate.schema() |> Keyword.delete(:sort),
+    auto_set_fields: [kind: :max]
+  }
+
+  @min %Spark.Dsl.Entity{
+    name: :min,
+    links: [
+      guides: [
+        "ash:guide:Aggregates"
+      ]
+    ],
+    describe: """
+    Declares a named `min` aggregate on the resource
+
+    Supports `filter`, but not `sort` (because that wouldn't affect the min)
+    """,
+    examples: [
+      """
+      min :first_assigned_ticket_subject, :assigned_tickets, :severity do
+        filter [active: true]
+      end
+      """
+    ],
+    target: Ash.Resource.Aggregate,
+    args: [:name, :relationship_path, :field],
+    schema: Ash.Resource.Aggregate.schema() |> Keyword.delete(:sort),
+    auto_set_fields: [kind: :min]
+  }
+
   @sum %Spark.Dsl.Entity{
     name: :sum,
     links: [
@@ -981,6 +1031,71 @@ defmodule Ash.Resource.Dsl do
     auto_set_fields: [kind: :sum]
   }
 
+  @avg %Spark.Dsl.Entity{
+    name: :avg,
+    links: [
+      guides: [
+        "ash:guide:Aggregates"
+      ]
+    ],
+    describe: """
+    Declares a named `avg` aggregate on the resource
+
+    Supports `filter`, but not `sort` (because that wouldn't affect the avg)
+    """,
+    examples: [
+      """
+      avg :assigned_ticket_price_sum, :assigned_tickets, :price do
+        filter [active: true]
+      end
+      """
+    ],
+    target: Ash.Resource.Aggregate,
+    args: [:name, :relationship_path, :field],
+    schema: Keyword.delete(Ash.Resource.Aggregate.schema(), :sort),
+    auto_set_fields: [kind: :avg]
+  }
+
+  @custom %Spark.Dsl.Entity{
+    name: :custom,
+    links: [
+      guides: [
+        "ash:guide:Aggregates"
+      ]
+    ],
+    describe: """
+    Declares a named `custom` aggregate on the resource
+
+    Supports `filter` and `sort`.
+
+    Custom aggregates provide an `implementation` which must implement data layer specific callbacks.
+
+    See the relevant data layer documentation for more.
+    """,
+    examples: [
+      """
+      custom :author_names, :authors, :string do
+        implementation {StringAgg, delimiter: ","}
+      end
+      """
+    ],
+    target: Ash.Resource.Aggregate,
+    args: [:name, :relationship_path, :type],
+    schema:
+      Ash.Resource.Aggregate.schema()
+      |> Keyword.put(:type,
+        type: :module,
+        required: true,
+        doc: "The type of the value returned by the aggregate"
+      )
+      |> Keyword.put(:implementation,
+        type: {:spark_behaviour, Ash.Resource.Aggregate.CustomAggregate},
+        required: true,
+        doc: "The module that implements the relevant data layer callbacks"
+      ),
+    auto_set_fields: [kind: :custom]
+  }
+
   @list %Spark.Dsl.Entity{
     name: :list,
     links: [
@@ -1034,7 +1149,11 @@ defmodule Ash.Resource.Dsl do
       @count,
       @first,
       @sum,
-      @list
+      @list,
+      @max,
+      @min,
+      @avg,
+      @custom
     ]
   }
 
diff --git a/lib/ash/resource/schema.ex b/lib/ash/resource/schema.ex
index 7324e684..9035d8ca 100644
--- a/lib/ash/resource/schema.ex
+++ b/lib/ash/resource/schema.ex
@@ -69,7 +69,11 @@ defmodule Ash.Schema do
 
           for aggregate <- Ash.Resource.Info.aggregates(__MODULE__),
               aggregate.name not in Ash.Resource.reserved_names() do
-            {:ok, type} = Aggregate.kind_to_type(aggregate.kind, :string)
+            if aggregate.kind == :custom do
+              {:ok, aggregate.type}
+            else
+              Aggregate.kind_to_type(aggregate.kind, :string)
+            end
 
             field(aggregate.name, Ash.Type.ecto_type(type), virtual: true)
 
@@ -161,7 +165,12 @@ defmodule Ash.Schema do
 
           for aggregate <- Ash.Resource.Info.aggregates(__MODULE__),
               aggregate.name not in Ash.Resource.reserved_names() do
-            {:ok, type} = Aggregate.kind_to_type(aggregate.kind, :string)
+            {:ok, type} =
+              if aggregate.kind == :custom do
+                {:ok, aggregate.type}
+              else
+                Aggregate.kind_to_type(aggregate.kind, :string)
+              end
 
             field(aggregate.name, Ash.Type.ecto_type(type), virtual: true)
 
diff --git a/test/resource/actions/create_test.exs b/test/resource/actions/create_test.exs
index 7cc3bd96..9ace1292 100644
--- a/test/resource/actions/create_test.exs
+++ b/test/resource/actions/create_test.exs
@@ -40,7 +40,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.CreateTest do
     test "it fails if `name` is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.CreateTest.Post]\n actions -> create -> default:\n  expected :name to be an atom, got: \"default\"",
+        "[Ash.Test.Dsl.Resource.Actions.CreateTest.Post]\n actions -> create -> default:\n  invalid value for :name option: expected atom, got: \"default\"",
         fn ->
           defposts do
             actions do
@@ -54,7 +54,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.CreateTest do
     test "it fails if `primary?` is not a boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.CreateTest.Post]\n actions -> create -> create:\n  expected :primary? to be a boolean, got: 10",
+        "[Ash.Test.Dsl.Resource.Actions.CreateTest.Post]\n actions -> create -> create:\n  invalid value for :primary? option: expected boolean, got: 10",
         fn ->
           defposts do
             actions do
diff --git a/test/resource/actions/destroy_test.exs b/test/resource/actions/destroy_test.exs
index 921ce497..51df5428 100644
--- a/test/resource/actions/destroy_test.exs
+++ b/test/resource/actions/destroy_test.exs
@@ -40,7 +40,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.DestroyTest do
     test "it fails if `name` is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.DestroyTest.Post]\n actions -> destroy -> default:\n  expected :name to be an atom, got: \"default\"",
+        "[Ash.Test.Dsl.Resource.Actions.DestroyTest.Post]\n actions -> destroy -> default:\n  invalid value for :name option: expected atom, got: \"default\"",
         fn ->
           defposts do
             actions do
@@ -54,7 +54,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.DestroyTest do
     test "it fails if `primary?` is not a boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.DestroyTest.Post]\n actions -> destroy -> destroy:\n  expected :primary? to be a boolean, got: 10",
+        "[Ash.Test.Dsl.Resource.Actions.DestroyTest.Post]\n actions -> destroy -> destroy:\n  invalid value for :primary? option: expected boolean, got: 10",
         fn ->
           defposts do
             actions do
diff --git a/test/resource/actions/read_test.exs b/test/resource/actions/read_test.exs
index 83d1d75d..2ab4ee25 100644
--- a/test/resource/actions/read_test.exs
+++ b/test/resource/actions/read_test.exs
@@ -40,7 +40,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.ReadTest do
     test "it fails if `name` is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.ReadTest.Post]\n actions -> read -> default:\n  expected :name to be an atom, got: \"default\"",
+        "[Ash.Test.Dsl.Resource.Actions.ReadTest.Post]\n actions -> read -> default:\n  invalid value for :name option: expected atom, got: \"default\"",
         fn ->
           defposts do
             actions do
@@ -54,7 +54,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.ReadTest do
     test "it fails if `primary?` is not a boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.ReadTest.Post]\n actions -> read -> read:\n  expected :primary? to be a boolean, got: 10",
+        "[Ash.Test.Dsl.Resource.Actions.ReadTest.Post]\n actions -> read -> read:\n  invalid value for :primary? option: expected boolean, got: 10",
         fn ->
           defposts do
             actions do
diff --git a/test/resource/actions/update_test.exs b/test/resource/actions/update_test.exs
index 18513dac..2f4168da 100644
--- a/test/resource/actions/update_test.exs
+++ b/test/resource/actions/update_test.exs
@@ -38,7 +38,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.UpdateTest do
     test "it fails if `name` is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.UpdateTest.Post]\n actions -> update -> default:\n  expected :name to be an atom, got: \"default\"",
+        "[Ash.Test.Dsl.Resource.Actions.UpdateTest.Post]\n actions -> update -> default:\n  invalid value for :name option: expected atom, got: \"default\"",
         fn ->
           defposts do
             actions do
@@ -52,7 +52,7 @@ defmodule Ash.Test.Dsl.Resource.Actions.UpdateTest do
     test "it fails if `primary?` is not a boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Dsl.Resource.Actions.UpdateTest.Post]\n actions -> update -> update:\n  expected :primary? to be a boolean, got: 10",
+        "[Ash.Test.Dsl.Resource.Actions.UpdateTest.Post]\n actions -> update -> update:\n  invalid value for :primary? option: expected boolean, got: 10",
         fn ->
           defposts do
             actions do
diff --git a/test/resource/attributes_test.exs b/test/resource/attributes_test.exs
index 2b4b78e5..81f296d1 100644
--- a/test/resource/attributes_test.exs
+++ b/test/resource/attributes_test.exs
@@ -53,7 +53,7 @@ defmodule Ash.Test.Resource.AttributesTest do
     test "raises if the attribute name is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.AttributesTest.Post]\n attributes -> attribute -> 10:\n  expected :name to be an atom, got: 10",
+        "[Ash.Test.Resource.AttributesTest.Post]\n attributes -> attribute -> 10:\n  invalid value for :name option: expected atom, got: 10",
         fn ->
           defposts do
             attributes do
@@ -67,7 +67,7 @@ defmodule Ash.Test.Resource.AttributesTest do
     test "raises if you pass an invalid value for `primary_key?`" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.AttributesTest.Post]\n attributes -> attribute -> foo:\n  expected :primary_key? to be a boolean, got: 10",
+        "[Ash.Test.Resource.AttributesTest.Post]\n attributes -> attribute -> foo:\n  invalid value for :primary_key? option: expected boolean, got: 10",
         fn ->
           defposts do
             attributes do
@@ -81,7 +81,7 @@ defmodule Ash.Test.Resource.AttributesTest do
     test "raises if you pass an invalid value for `private?`" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.AttributesTest.Post]\n attributes -> attribute -> foo:\n  expected :private? to be a boolean, got: \"an_invalid_value\"",
+        "[Ash.Test.Resource.AttributesTest.Post]\n attributes -> attribute -> foo:\n  invalid value for :private? option: expected boolean, got: \"an_invalid_value\"",
         fn ->
           defposts do
             attributes do
diff --git a/test/resource/relationships/belongs_to_test.exs b/test/resource/relationships/belongs_to_test.exs
index 49079f6a..b770e5ba 100644
--- a/test/resource/relationships/belongs_to_test.exs
+++ b/test/resource/relationships/belongs_to_test.exs
@@ -138,7 +138,7 @@ defmodule Ash.Test.Resource.Relationships.BelongsToTest do
     test "fails if destination_attribute is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  expected :destination_attribute to be an atom, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  invalid value for :destination_attribute option: expected atom, got: \"foo\"",
         fn ->
           defposts do
             relationships do
@@ -152,7 +152,7 @@ defmodule Ash.Test.Resource.Relationships.BelongsToTest do
     test "fails if source_attribute is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  expected :source_attribute to be an atom, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  invalid value for :source_attribute option: expected atom, got: \"foo\"",
         fn ->
           defposts do
             relationships do
@@ -166,7 +166,7 @@ defmodule Ash.Test.Resource.Relationships.BelongsToTest do
     test "fails if the destination is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  expected :destination to be an atom, got: \"foobar\"",
+        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  invalid value for :destination option: expected atom, got: \"foobar\"",
         fn ->
           defposts do
             relationships do
@@ -180,7 +180,7 @@ defmodule Ash.Test.Resource.Relationships.BelongsToTest do
     test "fails if the relationship name is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  expected :name to be an atom, got: \"foobar\"",
+        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  invalid value for :name option: expected atom, got: \"foobar\"",
         fn ->
           defposts do
             relationships do
@@ -194,7 +194,7 @@ defmodule Ash.Test.Resource.Relationships.BelongsToTest do
     test "fails if `primary_key?` is not a boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  expected :primary_key? to be a boolean, got: \"blah\"",
+        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  invalid value for :primary_key? option: expected boolean, got: \"blah\"",
         fn ->
           defposts do
             relationships do
@@ -208,7 +208,7 @@ defmodule Ash.Test.Resource.Relationships.BelongsToTest do
     test "fails if `private?` is not a boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  expected :private? to be a boolean, got: \"blah\"",
+        "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  invalid value for :private? option: expected boolean, got: \"blah\"",
         fn ->
           defposts do
             relationships do
@@ -223,7 +223,7 @@ defmodule Ash.Test.Resource.Relationships.BelongsToTest do
   test "fails if `define_attribute?` is not a boolean" do
     assert_raise(
       Spark.Error.DslError,
-      "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  expected :define_attribute? to be a boolean, got: \"blah\"",
+      "[Ash.Test.Resource.Relationships.BelongsToTest.Post]\n relationships -> belongs_to -> foobar:\n  invalid value for :define_attribute? option: expected boolean, got: \"blah\"",
       fn ->
         defposts do
           relationships do
diff --git a/test/resource/relationships/has_many_test.exs b/test/resource/relationships/has_many_test.exs
index 08b811e9..d27417e6 100644
--- a/test/resource/relationships/has_many_test.exs
+++ b/test/resource/relationships/has_many_test.exs
@@ -63,7 +63,7 @@ defmodule Ash.Test.Resource.Relationships.HasManyTest do
     test "fails if destination_attribute is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  expected :destination_attribute to be an atom, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  invalid value for :destination_attribute option: expected atom, got: \"foo\"",
         fn ->
           defposts do
             relationships do
@@ -77,7 +77,7 @@ defmodule Ash.Test.Resource.Relationships.HasManyTest do
     test "fails if source_attribute is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  expected :source_attribute to be an atom, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  invalid value for :source_attribute option: expected atom, got: \"foo\"",
         fn ->
           defposts do
             relationships do
@@ -91,7 +91,7 @@ defmodule Ash.Test.Resource.Relationships.HasManyTest do
     test "fails if the destination is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  expected :destination to be an atom, got: \"foobar\"",
+        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  invalid value for :destination option: expected atom, got: \"foobar\"",
         fn ->
           defposts do
             relationships do
@@ -105,7 +105,7 @@ defmodule Ash.Test.Resource.Relationships.HasManyTest do
     test "fails if the relationship name is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  expected :name to be an atom, got: \"foobar\"",
+        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  invalid value for :name option: expected atom, got: \"foobar\"",
         fn ->
           defposts do
             relationships do
@@ -119,7 +119,7 @@ defmodule Ash.Test.Resource.Relationships.HasManyTest do
     test "fails if private? is not an boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  expected :private? to be a boolean, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.HasManyTest.Post]\n relationships -> has_many -> foobar:\n  invalid value for :private? option: expected boolean, got: \"foo\"",
         fn ->
           defposts do
             relationships do
diff --git a/test/resource/relationships/has_one_test.exs b/test/resource/relationships/has_one_test.exs
index 2dc6acde..6791d0ec 100644
--- a/test/resource/relationships/has_one_test.exs
+++ b/test/resource/relationships/has_one_test.exs
@@ -63,7 +63,7 @@ defmodule Ash.Test.Resource.Relationships.HasOneTest do
     test "fails if destination_attribute is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  expected :destination_attribute to be an atom, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  invalid value for :destination_attribute option: expected atom, got: \"foo\"",
         fn ->
           defposts do
             relationships do
@@ -77,7 +77,7 @@ defmodule Ash.Test.Resource.Relationships.HasOneTest do
     test "fails if source_attribute is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  expected :source_attribute to be an atom, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  invalid value for :source_attribute option: expected atom, got: \"foo\"",
         fn ->
           defposts do
             relationships do
@@ -91,7 +91,7 @@ defmodule Ash.Test.Resource.Relationships.HasOneTest do
     test "fails if the destination is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  expected :destination to be an atom, got: \"foobar\"",
+        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  invalid value for :destination option: expected atom, got: \"foobar\"",
         fn ->
           defposts do
             relationships do
@@ -105,7 +105,7 @@ defmodule Ash.Test.Resource.Relationships.HasOneTest do
     test "fails if the relationship name is not an atom" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  expected :name to be an atom, got: \"foobar\"",
+        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  invalid value for :name option: expected atom, got: \"foobar\"",
         fn ->
           defposts do
             relationships do
@@ -119,7 +119,7 @@ defmodule Ash.Test.Resource.Relationships.HasOneTest do
     test "fails if private? is not an boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  expected :private? to be a boolean, got: \"foo\"",
+        "[Ash.Test.Resource.Relationships.HasOneTest.Post]\n relationships -> has_one -> foobar:\n  invalid value for :private? option: expected boolean, got: \"foo\"",
         fn ->
           defposts do
             relationships do
diff --git a/test/resource/relationships/many_to_many_test.exs b/test/resource/relationships/many_to_many_test.exs
index c430bfd3..bdd93d0f 100644
--- a/test/resource/relationships/many_to_many_test.exs
+++ b/test/resource/relationships/many_to_many_test.exs
@@ -102,7 +102,7 @@ defmodule Ash.Test.Resource.Relationships.ManyToManyTest do
     test "it fails if you pass a string to `through`" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  expected :through to be an atom, got: \"some_table\"",
+        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  invalid value for :through option: expected atom, got: \"some_table\"",
         fn ->
           defposts do
             relationships do
@@ -130,7 +130,7 @@ defmodule Ash.Test.Resource.Relationships.ManyToManyTest do
     test "it fails if you dont pass an atom for `source_attribute_on_join_resource`" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  expected :source_attribute_on_join_resource to be an atom, got: \"what\"",
+        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  invalid value for :source_attribute_on_join_resource option: expected atom, got: \"what\"",
         fn ->
           defposts do
             relationships do
@@ -147,7 +147,7 @@ defmodule Ash.Test.Resource.Relationships.ManyToManyTest do
     test "it fails if you dont pass an atom for `destination_attribute_on_join_resource`" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  expected :destination_attribute_on_join_resource to be an atom, got: \"what\"",
+        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  invalid value for :destination_attribute_on_join_resource option: expected atom, got: \"what\"",
         fn ->
           defposts do
             relationships do
@@ -164,7 +164,7 @@ defmodule Ash.Test.Resource.Relationships.ManyToManyTest do
     test "it fails if you dont pass an atom for `source_attribute`" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  expected :source_attribute to be an atom, got: \"what\"",
+        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  invalid value for :source_attribute option: expected atom, got: \"what\"",
         fn ->
           defposts do
             relationships do
@@ -182,7 +182,7 @@ defmodule Ash.Test.Resource.Relationships.ManyToManyTest do
     test "it fails if you dont pass an atom for `destination_attribute`" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  expected :destination_attribute to be an atom, got: \"what\"",
+        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  invalid value for :destination_attribute option: expected atom, got: \"what\"",
         fn ->
           defposts do
             relationships do
@@ -200,7 +200,7 @@ defmodule Ash.Test.Resource.Relationships.ManyToManyTest do
     test "fails if private? is not an boolean" do
       assert_raise(
         Spark.Error.DslError,
-        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  expected :private? to be a boolean, got: \"an_invalid_field\"",
+        "[Ash.Test.Resource.Relationships.ManyToManyTest.Post]\n relationships -> many_to_many -> foobars:\n  invalid value for :private? option: expected boolean, got: \"an_invalid_field\"",
         fn ->
           defposts do
             relationships do