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Fix CreateMessageRequestParams.Metadata type to JsonObject #1354

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Merged
stephentoub merged 4 commits into from
Feb 23, 2026
+34 −2
Merged

Fix CreateMessageRequestParams.Metadata type to JsonObject #1354

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834bd40
Initial plan
Copilot Feb 22, 2026
84765ac
Fix CreateMessageRequestParams.Metadata type from JsonElement? to Jso…
Copilot Feb 22, 2026
9463045
Add serialization roundtrip test for CreateMessageRequestParams.Metadata
Copilot Feb 22, 2026
0c5769f
Merge branch 'main' into copilot/fix-metadata-jsonobject-type
stephentoub Feb 22, 2026
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4 changes: 2 additions & 2 deletions src/ModelContextProtocol.Core/Protocol/CreateMessageRequestParams.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
using System.Diagnostics.CodeAnalysis;
using System.Text.Json;
using System.Text.Json.Nodes;
using System.Text.Json.Serialization;

namespace ModelContextProtocol.Protocol;
Expand Down Expand Up @@ -68,7 +68,7 @@ public sealed class CreateMessageRequestParams : RequestParams
/// </para>
/// </remarks>
[JsonPropertyName("metadata")]
public JsonElement? Metadata { get; set; }
public JsonObject? Metadata { get; set; }

/// <summary>
/// Gets or sets the server's preferences for which model to select.
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32 changes: 32 additions & 0 deletions tests/ModelContextProtocol.Tests/Protocol/CreateMessageRequestParamsTests.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
using ModelContextProtocol.Protocol;
using System.Text.Json;
using System.Text.Json.Nodes;

namespace ModelContextProtocol.Tests.Protocol;

Expand Down Expand Up @@ -166,6 +167,37 @@ public void WithToolChoiceNone_SerializationRoundtrips()
Assert.NotNull(deserialized.ToolChoice);
Assert.Equal("none", deserialized.ToolChoice.Mode);
}

[Fact]
public void WithMetadata_SerializationRoundtrips()
{
CreateMessageRequestParams requestParams = new()
{
MaxTokens = 500,
Messages =
[
new SamplingMessage
{
Role = Role.User,
Content = [new TextContentBlock { Text = "Hello" }]
}
],
Metadata = new JsonObject
{
["provider"] = "test-provider",
["custom_setting"] = 42
}
};

var json = JsonSerializer.Serialize(requestParams, McpJsonUtilities.DefaultOptions);
var deserialized = JsonSerializer.Deserialize<CreateMessageRequestParams>(json, McpJsonUtilities.DefaultOptions);

Assert.NotNull(deserialized);
Assert.Equal(500, deserialized.MaxTokens);
Assert.NotNull(deserialized.Metadata);
Assert.Equal("test-provider", (string?)deserialized.Metadata["provider"]);
Assert.Equal(42, (int)deserialized.Metadata["custom_setting"]!);
}
}


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