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Fix ToJsonObject serialization failure with anonymous types and add support for custom JsonSerializerOptions #1113

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Fix ToJsonObject serialization failure with anonymous types and add support for custom JsonSerializerOptions #1113

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982138e
Initial plan
Copilot Dec 18, 2025
6a070b3
Fix ToJsonObject to support anonymous types in dictionary values
Copilot Dec 18, 2025
57b4a93
Update McpJsonUtilitiesTests to reflect new anonymous type support
Copilot Dec 18, 2025
bcf2e24
Address code review feedback
Copilot Dec 18, 2025
7041a89
Address PR feedback: use GetTypeInfo instead of strongly-typed JsonCo…
Copilot Dec 18, 2025
867d044
Move anonymous type tests to existing AIContentExtensionsTests file
Copilot Dec 19, 2025
bd598ea
Add optional JsonSerializerOptions parameter to ToContentBlock and To…
Copilot Dec 19, 2025
32f2549
Add test for named user-defined types with source generation
Copilot Dec 19, 2025
cb95813
Add tests for anonymous types in CallToolAsync and ToChatMessage
Copilot Dec 19, 2025
a3cb705
Add optional JsonSerializerOptions parameter to ToChatMessage
Copilot Dec 19, 2025
111616b
Make JsonSerializerOptions parameter required for internal ToJsonObje…
Copilot Dec 19, 2025
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34 changes: 21 additions & 13 deletions src/ModelContextProtocol.Core/AIContentExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ public static class AIContentExtensions
chatResponse.FinishReason == ChatFinishReason.Length ? CreateMessageResult.StopReasonMaxTokens :
chatResponse.FinishReason == ChatFinishReason.ToolCalls ? CreateMessageResult.StopReasonToolUse :
chatResponse.FinishReason.ToString(),
Meta = chatResponse.AdditionalProperties?.ToJsonObject(),
Meta = chatResponse.AdditionalProperties?.ToJsonObject(McpJsonUtilities.DefaultOptions),
Role = lastMessage?.Role == ChatRole.User ? Role.User : Role.Assistant,
Content = contents,
};
Expand Down Expand Up @@ -138,8 +138,10 @@ public static class AIContentExtensions
}

/// <summary>Converts the specified dictionary to a <see cref="JsonObject"/>.</summary>
internal static JsonObject? ToJsonObject(this IReadOnlyDictionary<string, object?> properties) =>
JsonSerializer.SerializeToNode(properties, McpJsonUtilities.JsonContext.Default.IReadOnlyDictionaryStringObject) as JsonObject;
internal static JsonObject? ToJsonObject(this IReadOnlyDictionary<string, object?> properties, JsonSerializerOptions options)
{
return JsonSerializer.SerializeToNode(properties, options.GetTypeInfo(typeof(IReadOnlyDictionary<string, object?>))) as JsonObject;
}

internal static AdditionalPropertiesDictionary ToAdditionalProperties(this JsonObject obj)
{
Expand Down Expand Up @@ -181,6 +183,7 @@ public static ChatMessage ToChatMessage(this PromptMessage promptMessage)
/// </summary>
/// <param name="result">The tool result to convert.</param>
/// <param name="callId">The identifier for the function call request that triggered the tool invocation.</param>
/// <param name="options">The <see cref="JsonSerializerOptions"/> to use for serialization. If <see langword="null"/>, <see cref="McpJsonUtilities.DefaultOptions"/> is used.</param>
/// <returns>A <see cref="ChatMessage"/> object created from the tool result.</returns>
/// <remarks>
/// This method transforms a protocol-specific <see cref="CallToolResult"/> from the Model Context Protocol
Expand All @@ -189,12 +192,14 @@ public static ChatMessage ToChatMessage(this PromptMessage promptMessage)
/// serialized <see cref="JsonElement"/>.
/// </remarks>
/// <exception cref="ArgumentNullException"><paramref name="result"/> or <paramref name="callId"/> is <see langword="null"/>.</exception>
public static ChatMessage ToChatMessage(this CallToolResult result, string callId)
public static ChatMessage ToChatMessage(this CallToolResult result, string callId, JsonSerializerOptions? options = null)
{
Throw.IfNull(result);
Throw.IfNull(callId);

return new(ChatRole.Tool, [new FunctionResultContent(callId, JsonSerializer.SerializeToElement(result, McpJsonUtilities.JsonContext.Default.CallToolResult))
options ??= McpJsonUtilities.DefaultOptions;

return new(ChatRole.Tool, [new FunctionResultContent(callId, JsonSerializer.SerializeToElement(result, options.GetTypeInfo<CallToolResult>()))
{
RawRepresentation = result,
}]);
Expand Down Expand Up @@ -271,7 +276,7 @@ public static IList<PromptMessage> ToPromptMessages(this ChatMessage chatMessage
EmbeddedResourceBlock resourceContent => resourceContent.Resource.ToAIContent(),

ToolUseContentBlock toolUse => FunctionCallContent.CreateFromParsedArguments(toolUse.Input, toolUse.Id, toolUse.Name,
static json => JsonSerializer.Deserialize(json, McpJsonUtilities.JsonContext.Default.IDictionaryStringObject)),
static json => JsonSerializer.Deserialize(json, McpJsonUtilities.DefaultOptions.GetTypeInfo<IDictionary<string, object?>>())),

ToolResultContentBlock toolResult => new FunctionResultContent(
toolResult.ToolUseId,
Expand Down Expand Up @@ -365,12 +370,15 @@ public static IList<AIContent> ToAIContents(this IEnumerable<ResourceContents> c

/// <summary>Creates a new <see cref="ContentBlock"/> from the content of an <see cref="AIContent"/>.</summary>
/// <param name="content">The <see cref="AIContent"/> to convert.</param>
/// <param name="options">The <see cref="JsonSerializerOptions"/> to use for serialization. If <see langword="null"/>, <see cref="McpJsonUtilities.DefaultOptions"/> is used.</param>
/// <returns>The created <see cref="ContentBlock"/>.</returns>
/// <exception cref="ArgumentNullException"><paramref name="content"/> is <see langword="null"/>.</exception>
public static ContentBlock ToContentBlock(this AIContent content)
public static ContentBlock ToContentBlock(this AIContent content, JsonSerializerOptions? options = null)
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@eiriktsarpalis eiriktsarpalis Dec 19, 2025

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@stephentoub how concerned are we about this kind of breaking change? Should we change this to be a new overload?

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@stephentoub stephentoub Dec 19, 2025

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We'll need to avoid making these very soon, but for now I think it's ok.

{
Throw.IfNull(content);

options ??= McpJsonUtilities.DefaultOptions;

ContentBlock contentBlock = content switch
{
TextContent textContent => new TextContentBlock
Expand Down Expand Up @@ -404,27 +412,27 @@ public static ContentBlock ToContentBlock(this AIContent content)
{
Id = callContent.CallId,
Name = callContent.Name,
Input = JsonSerializer.SerializeToElement(callContent.Arguments, McpJsonUtilities.DefaultOptions.GetTypeInfo<IDictionary<string, object?>>()!),
Input = JsonSerializer.SerializeToElement(callContent.Arguments, options.GetTypeInfo<IDictionary<string, object?>>()!),
},

FunctionResultContent resultContent => new ToolResultContentBlock()
{
ToolUseId = resultContent.CallId,
IsError = resultContent.Exception is not null,
Content =
resultContent.Result is AIContent c ? [c.ToContentBlock()] :
resultContent.Result is IEnumerable<AIContent> ec ? [.. ec.Select(c => c.ToContentBlock())] :
[new TextContentBlock { Text = JsonSerializer.Serialize(content, McpJsonUtilities.DefaultOptions.GetTypeInfo<object>()) }],
resultContent.Result is AIContent c ? [c.ToContentBlock(options)] :
resultContent.Result is IEnumerable<AIContent> ec ? [.. ec.Select(c => c.ToContentBlock(options))] :
[new TextContentBlock { Text = JsonSerializer.Serialize(content, options.GetTypeInfo<object>()) }],
StructuredContent = resultContent.Result is JsonElement je ? je : null,
},

_ => new TextContentBlock
{
Text = JsonSerializer.Serialize(content, McpJsonUtilities.DefaultOptions.GetTypeInfo(typeof(object))),
Text = JsonSerializer.Serialize(content, options.GetTypeInfo(typeof(object))),
}
};

contentBlock.Meta = content.AdditionalProperties?.ToJsonObject();
contentBlock.Meta = content.AdditionalProperties?.ToJsonObject(options);

return contentBlock;
}
Expand Down
4 changes: 2 additions & 2 deletions src/ModelContextProtocol.Core/Server/McpServer.Methods.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -148,7 +148,7 @@ public async Task<ChatResponse> SampleAsync(
Name = af.Name,
Description = af.Description,
InputSchema = af.JsonSchema,
Meta = af.AdditionalProperties.ToJsonObject(),
Meta = af.AdditionalProperties.ToJsonObject(McpJsonUtilities.DefaultOptions),
});
}
}
Expand All @@ -172,7 +172,7 @@ public async Task<ChatResponse> SampleAsync(
Temperature = chatOptions?.Temperature,
ToolChoice = toolChoice,
Tools = tools,
Meta = chatOptions?.AdditionalProperties?.ToJsonObject(),
Meta = chatOptions?.AdditionalProperties?.ToJsonObject(McpJsonUtilities.DefaultOptions),
}, cancellationToken).ConfigureAwait(false);

List<AIContent> responseContents = [];
Expand Down
4 changes: 2 additions & 2 deletions src/ModelContextProtocol.Core/Server/McpServerTool.cs
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Expand Up @@ -99,7 +99,7 @@ namespace ModelContextProtocol.Server;
/// </item>
/// <item>
/// <term><see cref="AIContent"/></term>
/// <description>Converted to a single <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent)"/>.</description>
/// <description>Converted to a single <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent, JsonSerializerOptions)"/>.</description>
/// </item>
/// <item>
/// <term><see cref="string"/></term>
Expand All @@ -111,7 +111,7 @@ namespace ModelContextProtocol.Server;
/// </item>
/// <item>
/// <term><see cref="IEnumerable{AIContent}"/> of <see cref="AIContent"/></term>
/// <description>Each <see cref="AIContent"/> is converted to a <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent)"/>.</description>
/// <description>Each <see cref="AIContent"/> is converted to a <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent, JsonSerializerOptions)"/>.</description>
/// </item>
/// <item>
/// <term><see cref="IEnumerable{ContentBlock}"/> of <see cref="ContentBlock"/></term>
Expand Down
4 changes: 2 additions & 2 deletions src/ModelContextProtocol.Core/Server/McpServerToolAttribute.cs
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Expand Up @@ -90,7 +90,7 @@ namespace ModelContextProtocol.Server;
/// </item>
/// <item>
/// <term><see cref="AIContent"/></term>
/// <description>Converted to a single <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent)"/>.</description>
/// <description>Converted to a single <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent, JsonSerializerOptions)"/>.</description>
/// </item>
/// <item>
/// <term><see cref="string"/></term>
Expand All @@ -106,7 +106,7 @@ namespace ModelContextProtocol.Server;
/// </item>
/// <item>
/// <term><see cref="IEnumerable{AIContent}"/> of <see cref="AIContent"/></term>
/// <description>Each <see cref="AIContent"/> is converted to a <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent)"/>.</description>
/// <description>Each <see cref="AIContent"/> is converted to a <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent, JsonSerializerOptions)"/>.</description>
/// </item>
/// <item>
/// <term><see cref="IEnumerable{Content}"/> of <see cref="ContentBlock"/></term>
Expand Down
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