feat: add function property attribute

src/AnthropicClient/Models/FunctionPropertyAttribute.cs

@@ -0,0 +1,49 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Attribute to describe a property of a type that is used as a function parameter.
+/// </summary>
+[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field)]
+public class FunctionPropertyAttribute : Attribute
+{
+  /// <summary>
+  /// Description of the property.
+  /// </summary>
+  public string Description { get; } = string.Empty;
+
+  /// <summary>
+  /// Whether the property is required.
+  /// </summary>
+  public bool Required { get; } = false;
+
+  /// <summary>
+  /// Default value of the property.
+  /// </summary>
+  public object? DefaultValue { get; } = null;
+
+  /// <summary>
+  /// Possible values of the property.
+  /// </summary>
+  public object[]? PossibleValues { get; } = null;
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="FunctionPropertyAttribute"/> class.
+  /// </summary>
+  /// <param name="description">Description of the property.</param>
+  /// <param name="required">Whether the property is required.</param>
+  /// <param name="defaultValue">Default value of the property.</param>
+  /// <param name="possibleValues">Possible values of the property.</param>
+  /// <returns>A new instance of the <see cref="FunctionPropertyAttribute"/> class.</returns>
+  public FunctionPropertyAttribute(
+    string description,
+    bool required = false,
+    object? defaultValue = null,
+    object[]? possibleValues = null
+  )
+  {
+    Description = description;
+    Required = required;
+    DefaultValue = defaultValue;
+    PossibleValues = possibleValues;
+  }
+}

src/AnthropicClient/Utils/JsonSchemaGenerator.cs

@@ -1,7 +1,9 @@
 using System.Reflection;
+using System.Text.Json;
 using System.Text.Json.Nodes;
 
 using AnthropicClient.Models;
+using AnthropicClient.Json;
 
 namespace AnthropicClient.Utils;
 
@@ -179,15 +181,11 @@ static class JsonSchemaGenerator
         _ => throw new InvalidOperationException("Member is not a property or field")
       };
 
-      // TODO: Provide attribute to allow specifying...
-      // 1. Name
-      // 2. Description
-      // 3. Required
-      // 4. Default values
-      // 5. Possible values
+      var attribute = member.GetCustomAttribute<FunctionPropertyAttribute>();
+
       var memberPropertyName = member.Name;
-      var memberDescription = string.Empty;
-      var memberRequired = Nullable.GetUnderlyingType(memberType) is null;
+      var memberDescription = attribute?.Description ?? string.Empty;
+      var memberRequired = attribute?.Required ?? Nullable.GetUnderlyingType(memberType) is null;
 
       memberProperty = definitions.AsObject().ContainsKey(memberType.FullName)
         ? new JsonObject()
@@ -201,6 +199,38 @@ static class JsonSchemaGenerator
         memberRequiredProperties.Add(memberPropertyName);
       }
 
+      JsonNode? defaultValue = null;
+
+      if (attribute?.DefaultValue is not null)
+      {
+        defaultValue = JsonNode.Parse(JsonSerializer.Serialize(attribute.DefaultValue, JsonSerializationOptions.DefaultOptions));
+        memberProperty["default"] = defaultValue;
+      }
+
+      if (attribute?.PossibleValues is { Length: > 0 })
+      {
+        var enumValues = new JsonArray();
+
+        foreach (var value in attribute.PossibleValues)
+        {
+          var enumValue = JsonNode.Parse(JsonSerializer.Serialize(value, JsonSerializationOptions.DefaultOptions));
+
+          if (defaultValue is null || JsonNode.DeepEquals(enumValue, defaultValue) is false)
+          {
+            enumValues.Add(enumValue);
+          }
+        }
+
+        var containsDefaultValue = enumValues.Where(value => JsonNode.DeepEquals(value, defaultValue)).Any();
+
+        if (defaultValue is not null && containsDefaultValue is false)
+        {
+          enumValues.Add(JsonNode.Parse(defaultValue.ToJsonString(JsonSerializationOptions.DefaultOptions)));
+        }
+
+        memberProperty[EnumKey] = enumValues;
+      }
+
       memberProperty[DescriptionKey] = memberDescription;
       memberProperties[memberPropertyName] = memberProperty;
     }

tests/AnthropicClient.Tests/Unit/Utils/JsonSchemaGeneratorTestData.cs

@@ -868,6 +868,64 @@ public class JsonSchemaGeneratorTestData : IEnumerable<object[]>
         },
       }
     };
+
+    // complex type with attributes
+    yield return new object[]
+    {
+      Tool.CreateFromFunction(TestToolName,TestToolDescription,(Rule rule) => rule),
+      new JsonObject()
+      {
+        ["type"] = "object",
+        ["definitions"] = new JsonObject()
+        {
+          [$"{typeof(Rule).FullName}"] = new JsonObject()
+          {
+            ["type"] = "object",
+            ["properties"] = new JsonObject()
+            {
+              ["Status"] = new JsonObject()
+              {
+                ["type"] = "string",
+                ["description"] = "Indicates the current status of the rule.",
+                ["default"] = "Active",
+                ["enum"] = new JsonArray()
+                {
+                  "Inactive",
+                  "Active",
+                }
+              },
+              ["Type"] = new JsonObject()
+              {
+                ["type"] = "string",
+                ["description"] = "The type of the rule.",
+                ["default"] = "Type A",
+                ["enum"] = new JsonArray()
+                {
+                  "Type B",
+                  "Type A",
+                }
+              }
+            },
+            ["required"] = new JsonArray()
+            {
+              "Status"
+            }
+          }
+        },
+        ["properties"] = new JsonObject()
+        {
+          ["rule"] = new JsonObject()
+          {
+            ["$ref"] = $"#/definitions/{typeof(Rule).FullName}",
+            ["description"] = string.Empty
+          }
+        },
+        ["required"] = new JsonArray()
+        {
+          "rule",
+        },
+      }
+    };
   }
 
   IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
@@ -902,3 +960,22 @@ class Dad
 {
   public string Role = "Father";
 }
+
+class Rule
+{
+  [FunctionProperty(
+    "Indicates the current status of the rule.",
+    true,
+    "Active",
+    new object[] { "Active", "Inactive" }
+  )]
+  public string Status { get; } = "Active";
+
+  [FunctionProperty(
+    "The type of the rule.",
+    false,
+    "Type A",
+    new object[] { "Type B" }
+  )]
+  public string Type { get; } = "Type A";
+}