Replace AIFunctionParameterMetadata with MethodInfo

src/Libraries/Microsoft.Extensions.AI.Abstractions/Functions/AIFunctionMetadata.cs

@@ -4,7 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.Linq;
+using System.Reflection;
 using System.Text.Json;
 using Microsoft.Shared.Collections;
 using Microsoft.Shared.Diagnostics;
@@ -25,18 +25,9 @@ public sealed class AIFunctionMetadata
     /// <summary>The JSON schema describing the function and its input parameters.</summary>
     private readonly JsonElement _schema = AIJsonUtilities.DefaultJsonSchema;
 
-    /// <summary>The function's parameters.</summary>
-    private readonly IReadOnlyList<AIFunctionParameterMetadata> _parameters = [];
-
-    /// <summary>The function's return parameter.</summary>
-    private readonly AIFunctionReturnParameterMetadata _returnParameter = AIFunctionReturnParameterMetadata.Empty;
-
     /// <summary>Optional additional properties in addition to the named properties already available on this class.</summary>
     private readonly IReadOnlyDictionary<string, object?> _additionalProperties = EmptyReadOnlyDictionary<string, object?>.Instance;
 
-    /// <summary><see cref="_parameters"/> indexed by name, lazily initialized.</summary>
-    private Dictionary<string, AIFunctionParameterMetadata>? _parametersByName;
-
     /// <summary>Initializes a new instance of the <see cref="AIFunctionMetadata"/> class for a function with the specified name.</summary>
     /// <param name="name">The name of the function.</param>
     /// <exception cref="ArgumentNullException">The <paramref name="name"/> was null.</exception>
@@ -48,15 +39,13 @@ public AIFunctionMetadata(string name)
     /// <summary>Initializes a new instance of the <see cref="AIFunctionMetadata"/> class as a copy of another <see cref="AIFunctionMetadata"/>.</summary>
     /// <exception cref="ArgumentNullException">The <paramref name="metadata"/> was null.</exception>
     /// <remarks>
-    /// This creates a shallow clone of <paramref name="metadata"/>. The new instance's <see cref="Parameters"/> and
-    /// <see cref="ReturnParameter"/> properties will return the same objects as in the original instance.
+    /// This creates a shallow clone of <paramref name="metadata"/>.
     /// </remarks>
     public AIFunctionMetadata(AIFunctionMetadata metadata)
     {
         Name = Throw.IfNull(metadata).Name;
         Description = metadata.Description;
-        Parameters = metadata.Parameters;
-        ReturnParameter = metadata.ReturnParameter;
+        UnderlyingMethod = metadata.UnderlyingMethod;
         AdditionalProperties = metadata.AdditionalProperties;
         Schema = metadata.Schema;
     }
@@ -76,33 +65,15 @@ public string Description
         init => _description = value ?? string.Empty;
     }
 
-    /// <summary>Gets the metadata for the parameters to the function.</summary>
-    /// <remarks>If the function has no parameters, the returned list is empty.</remarks>
-    public IReadOnlyList<AIFunctionParameterMetadata> Parameters
-    {
-        get => _parameters;
-        init => _parameters = Throw.IfNull(value);
-    }
-
-    /// <summary>Gets the <see cref="AIFunctionParameterMetadata"/> for a parameter by its name.</summary>
-    /// <param name="name">The name of the parameter.</param>
-    /// <returns>The corresponding <see cref="AIFunctionParameterMetadata"/>, if found; otherwise, null.</returns>
-    public AIFunctionParameterMetadata? GetParameter(string name)
-    {
-        Dictionary<string, AIFunctionParameterMetadata>? parametersByName = _parametersByName ??= _parameters.ToDictionary(p => p.Name);
-
-        return parametersByName.TryGetValue(name, out AIFunctionParameterMetadata? parameter) ?
-            parameter :
-            null;
-    }
-
-    /// <summary>Gets parameter metadata for the return parameter.</summary>
-    /// <remarks>If the function has no return parameter, the value is a default instance of an <see cref="AIFunctionReturnParameterMetadata"/>.</remarks>
-    public AIFunctionReturnParameterMetadata ReturnParameter
-    {
-        get => _returnParameter;
-        init => _returnParameter = Throw.IfNull(value);
-    }
+    /// <summary>
+    /// Gets a <see cref="MethodInfo"/> for the underlying .NET method this <see cref="AIFunction"/> represents.
+    /// </summary>
+    /// <remarks>
+    /// This property provides additional metadata on the function and its signature.
+    /// Setting this property is optional and should have no impact on function invocation or its JSON schema,
+    /// which is how <see cref="IChatClient"/> implementations interface with AI functions primarily.
+    /// </remarks>
+    public MethodInfo? UnderlyingMethod { get; init; }
 
     /// <summary>Gets a JSON Schema describing the function and its input parameters.</summary>
     /// <remarks>
@@ -124,8 +95,6 @@ public AIFunctionReturnParameterMetadata ReturnParameter
     /// </code>
     /// <para>
     /// The metadata present in the schema document plays an important role in guiding AI function invocation.
-    /// Functions should incorporate as much detail as possible. The arity of the "properties" keyword should
-    /// also match the length of the <see cref="Parameters"/> list.
     /// </para>
     /// <para>
     /// When no schema is specified, consuming chat clients should assume the "{}" or "true" schema, indicating that any JSON input is admissible.

src/Libraries/Microsoft.Extensions.AI.Abstractions/Utilities/AIJsonUtilities.Schema.cs

@@ -2,11 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
-using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Text.Json;
 using System.Text.Json.Nodes;
@@ -46,39 +46,47 @@ public static partial class AIJsonUtilities
     private static readonly string[] _schemaKeywordsDisallowedByAIVendors = ["minLength", "maxLength", "pattern", "format"];
 
     /// <summary>
-    /// Determines a JSON schema for the provided AI function parameter metadata.
+    /// Determines a JSON schema for the provided method signature.
     /// </summary>
+    /// <param name="methodInfo">The method from which to extract schema information.</param>
     /// <param name="title">The title keyword used by the method schema.</param>
     /// <param name="description">The description keyword used by the method schema.</param>
-    /// <param name="parameters">The AI function parameter metadata.</param>
     /// <param name="serializerOptions">The options used to extract the schema from the specified type.</param>
     /// <param name="inferenceOptions">The options controlling schema inference.</param>
     /// <returns>A JSON schema document encoded as a <see cref="JsonElement"/>.</returns>
     public static JsonElement CreateFunctionJsonSchema(
+        MethodBase methodInfo,
         string? title = null,
         string? description = null,
-        IReadOnlyList<AIFunctionParameterMetadata>? parameters = null,
         JsonSerializerOptions? serializerOptions = null,
         AIJsonSchemaCreateOptions? inferenceOptions = null)
     {
+        _ = Throw.IfNull(methodInfo);
         serializerOptions ??= DefaultOptions;
         inferenceOptions ??= AIJsonSchemaCreateOptions.Default;
+        title ??= methodInfo.Name;
+        description ??= methodInfo.GetCustomAttribute<DescriptionAttribute>()?.Description;
 
         JsonObject parameterSchemas = new();
         JsonArray? requiredProperties = null;
-        foreach (AIFunctionParameterMetadata parameter in parameters ?? [])
+        foreach (ParameterInfo parameter in methodInfo.GetParameters())
         {
+            if (string.IsNullOrWhiteSpace(parameter.Name))
+            {
+                Throw.ArgumentException(nameof(parameter), "Parameter is missing a name.");
+            }
+
             JsonNode parameterSchema = CreateJsonSchemaCore(
-                parameter.ParameterType,
-                parameter.Name,
-                parameter.Description,
-                parameter.HasDefaultValue,
-                parameter.DefaultValue,
+                type: parameter.ParameterType,
+                parameterName: parameter.Name,
+                description: parameter.GetCustomAttribute<DescriptionAttribute>(inherit: true)?.Description,
+                hasDefaultValue: parameter.HasDefaultValue,
+                defaultValue: parameter.HasDefaultValue ? parameter.DefaultValue : null,
                 serializerOptions,
                 inferenceOptions);
 
             parameterSchemas.Add(parameter.Name, parameterSchema);
-            if (parameter.IsRequired)
+            if (!parameter.IsOptional)
             {
                 (requiredProperties ??= []).Add((JsonNode)parameter.Name);
             }

src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIModelMapper.ChatCompletion.cs

@@ -26,8 +26,6 @@ namespace Microsoft.Extensions.AI;
 
 internal static partial class OpenAIModelMappers
 {
-    internal static JsonElement DefaultParameterSchema { get; } = JsonDocument.Parse("{}").RootElement;
-
     public static ChatCompletion ToOpenAIChatCompletion(ChatResponse response, JsonSerializerOptions options)
     {
         _ = Throw.IfNull(response);
@@ -418,26 +416,11 @@ private static AITool FromOpenAIChatTool(ChatTool chatTool)
         }
 
         OpenAIChatToolJson openAiChatTool = JsonSerializer.Deserialize(chatTool.FunctionParameters.ToMemory().Span, OpenAIJsonContext.Default.OpenAIChatToolJson)!;
-        List<AIFunctionParameterMetadata> parameters = new(openAiChatTool.Properties.Count);
-        foreach (KeyValuePair<string, JsonElement> property in openAiChatTool.Properties)
-        {
-            parameters.Add(new(property.Key)
-            {
-                IsRequired = openAiChatTool.Required.Contains(property.Key),
-            });
-        }
-
         AIFunctionMetadata metadata = new(chatTool.FunctionName)
         {
             Description = chatTool.FunctionDescription,
             AdditionalProperties = additionalProperties,
-            Parameters = parameters,
             Schema = JsonSerializer.SerializeToElement(openAiChatTool, OpenAIJsonContext.Default.OpenAIChatToolJson),
-            ReturnParameter = new()
-            {
-                Description = "Return parameter",
-                Schema = DefaultParameterSchema,
-            }
         };
 
         return new MetadataOnlyAIFunction(metadata);