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Change type of Tool.InputSchema to be JsonElement (#4)

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* Change type of Tool.InputSchema to be JsonElement

* Add schema validation in the InputSchema property setter.

* Simplify AIFunction tool adapter.

---------

Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
This commit is contained in:
Stephen Toub 2025-03-20 13:16:41 -04:00 • committed by GitHub
commit 3de19d38e4
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GPG key ID: B5690EEEBB952194
6 changed files with 175 additions and 128 deletions
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12
src/ModelContextProtocol/Client/McpClientExtensions.cs
View file

@ -466,8 +466,6 @@ public static class McpClientExtensions
/// <summary>Provides an AI function that calls a tool through <see cref="IMcpClient"/>.</summary>
private sealed class McpAIFunction(IMcpClient client, Tool tool) : AIFunction
{
private JsonElement? _jsonSchema;
/// <inheritdoc/>
public override string Name => tool.Name;
@ -475,15 +473,7 @@ public static class McpClientExtensions
public override string Description => tool.Description ?? string.Empty;
/// <inheritdoc/>
public override JsonElement JsonSchema => _jsonSchema ??=
JsonSerializer.SerializeToElement(new Dictionary<string, object>
{
["type"] = "object",
["title"] = tool.Name,
["description"] = tool.Description ?? string.Empty,
["properties"] = tool.InputSchema?.Properties ?? [],
["required"] = tool.InputSchema?.Required ?? []
}, McpJsonUtilities.JsonContext.Default.DictionaryStringObject);
public override JsonElement JsonSchema => tool.InputSchema;
/// <inheritdoc/>
protected async override Task<object?> InvokeCoreAsync(

2
src/ModelContextProtocol/Configuration/McpServerBuilderExtensions.Tools.cs
View file

@ -96,7 +96,7 @@ public static partial class McpServerBuilderExtensions
{
Name = function.Name,
Description = function.Description,
InputSchema = JsonSerializer.Deserialize(function.JsonSchema, McpJsonUtilities.JsonContext.Default.JsonSchema),
InputSchema = function.JsonSchema,
});
callbacks.Add(function.Name, async (request, cancellationToken) =>

26
src/ModelContextProtocol/Protocol/Types/JsonSchema.cs
View file

@ -1,26 +0,0 @@
namespace ModelContextProtocol.Protocol.Types;
/// <summary>
/// Represents a JSON schema for a tool's input arguments.
/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
/// </summary>
public class JsonSchema
{
/// <summary>
/// The type of the schema, should be "object".
/// </summary>
[System.Text.Json.Serialization.JsonPropertyName("type")]
public string Type { get; set; } = "object";
/// <summary>
/// Map of property names to property definitions.
/// </summary>
[System.Text.Json.Serialization.JsonPropertyName("properties")]
public Dictionary<string, JsonSchemaProperty>? Properties { get; set; }
/// <summary>
/// List of required property names.
/// </summary>
[System.Text.Json.Serialization.JsonPropertyName("required")]
public List<string>? Required { get; set; }
}

20
src/ModelContextProtocol/Protocol/Types/JsonSchemaProperty.cs
View file

@ -1,20 +0,0 @@
namespace ModelContextProtocol.Protocol.Types;
/// <summary>
/// Represents a property in a JSON schema.
/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
/// </summary>
public class JsonSchemaProperty
{
/// <summary>
/// The type of the property. Should be a JSON Schema type and is required.
/// </summary>
[System.Text.Json.Serialization.JsonPropertyName("type")]
public string Type { get; set; } = string.Empty;
/// <summary>
/// A human-readable description of the property.
/// </summary>
[System.Text.Json.Serialization.JsonPropertyName("description")]
public string? Description { get; set; } = string.Empty;
}

23
src/ModelContextProtocol/Protocol/Types/Tool.cs
View file

@ -1,4 +1,6 @@
using System.Text.Json.Serialization;
using ModelContextProtocol.Utils.Json;
using System.Text.Json;
using System.Text.Json.Serialization;
namespace ModelContextProtocol.Protocol.Types;
@ -23,6 +25,23 @@ public class Tool
/// <summary>
/// A JSON Schema object defining the expected parameters for the tool.
/// </summary>
/// <remarks>
/// Needs to a valid JSON schema object that additionally is of type object.
/// </remarks>
[JsonPropertyName("inputSchema")]
public JsonSchema? InputSchema { get; set; }
public JsonElement InputSchema
{
get => _inputSchema;
set
{
if (!McpJsonUtilities.IsValidMcpToolSchema(value))
{
throw new ArgumentException("The specified document is not a valid MPC tool JSON schema.", nameof(InputSchema));
}
_inputSchema = value;
}
}
private JsonElement _inputSchema = McpJsonUtilities.DefaultMcpToolSchema;
}

33
src/ModelContextProtocol/Utils/Json/McpJsonUtilities.cs
View file

@ -77,6 +77,31 @@ public static partial class McpJsonUtilities
internal static JsonTypeInfo<T> GetTypeInfo<T>(this JsonSerializerOptions options) =>
(JsonTypeInfo<T>)options.GetTypeInfo(typeof(T));
internal static JsonElement DefaultMcpToolSchema = ParseJsonElement("{\"type\":\"object\"}"u8);
internal static bool IsValidMcpToolSchema(JsonElement element)
{
if (element.ValueKind is not JsonValueKind.Object)
{
return false;
}
foreach (JsonProperty property in element.EnumerateObject())
{
if (property.NameEquals("type"))
{
if (property.Value.ValueKind is not JsonValueKind.String ||
!property.Value.ValueEquals("object"))
{
return false;
}
return true; // No need to check other properties
}
}
return false; // No type keyword found.
}
// Keep in sync with CreateDefaultOptions above.
[JsonSourceGenerationOptions(JsonSerializerDefaults.Web,
UseStringEnumConverter = true,
@ -96,7 +121,13 @@ public static partial class McpJsonUtilities
[JsonSerializable(typeof(CreateMessageResult))]
[JsonSerializable(typeof(ListRootsResult))]
[JsonSerializable(typeof(InitializeResult))]
[JsonSerializable(typeof(JsonSchema))]
[JsonSerializable(typeof(CallToolResponse))]
internal sealed partial class JsonContext : JsonSerializerContext;
private static JsonElement ParseJsonElement(ReadOnlySpan<byte> utf8Json)
{
Utf8JsonReader reader = new(utf8Json);
return JsonElement.ParseValue(ref reader);
}
}