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Update McpErrorCode XML docs and fix error code usage to align with MCP spec (#1291)

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
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Copilot 2026-02-17 13:12:29 -08:00 • committed by GitHub
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2 changed files with 30 additions and 17 deletions
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27
src/ModelContextProtocol.Core/McpErrorCode.cs
View file

@ -39,10 +39,19 @@ public enum McpErrorCode
InvalidRequest = -32600,
/// <summary>
/// Indicates that the requested method does not exist or is not available on the server.
/// Indicates that the requested method does not exist or is not available.
/// </summary>
/// <remarks>
/// This error is returned when the method name specified in the request cannot be found.
/// <para>
/// In MCP, this error is returned when a request is made for a method that requires a capability
/// that has not been declared. This can occur in either direction:
/// </para>
/// <list type="bullet">
/// <item><description>A server returning this error when the client requests a capability it doesn't support
/// (for example, requesting completions when the <c>completions</c> capability was not advertised).</description></item>
/// <item><description>A client returning this error when the server requests a capability it doesn't support
/// (for example, requesting roots when the client did not declare the <c>roots</c> capability).</description></item>
/// </list>
/// </remarks>
MethodNotFound = -32601,
@ -51,15 +60,19 @@ public enum McpErrorCode
/// </summary>
/// <remarks>
/// <para>
/// This error is returned for protocol-level parameter issues, such as:
/// In MCP, this error is returned for protocol-level parameter validation failures in various contexts:
/// </para>
/// <list type="bullet">
/// <item><description>Malformed requests that fail to satisfy the request schema (for example, CallToolRequest)</description></item>
/// <item><description>Unknown or unrecognized primitive names (for example, tool, prompt, or resource names)</description></item>
/// <item><description>Missing required protocol-level parameters</description></item>
/// <item><description><b>Tools</b>: Unknown tool name or invalid protocol-level tool arguments.</description></item>
/// <item><description><b>Prompts</b>: Unknown prompt name or missing required protocol-level arguments.</description></item>
/// <item><description><b>Pagination</b>: Invalid or expired cursor values.</description></item>
/// <item><description><b>Logging</b>: Invalid log level.</description></item>
/// <item><description><b>Tasks</b>: Invalid or nonexistent task ID or invalid cursor.</description></item>
/// <item><description><b>Elicitation</b>: Server requests an elicitation mode not declared in client capabilities.</description></item>
/// <item><description><b>Sampling</b>: Missing tool result or tool results mixed with other content.</description></item>
/// </list>
/// <para>
/// Note: Input validation errors within tool/prompt/resource arguments should be reported as execution errors
/// Note: Application-layer validation errors within tool/prompt/resource arguments should be reported as execution errors
/// (for example, via <see cref="Protocol.CallToolResult.IsError"/>) rather than as protocol errors, allowing language
/// models to receive error feedback and self-correct.
/// </para>

4
src/ModelContextProtocol.Core/Server/McpServerImpl.cs
View file

@ -591,7 +591,7 @@ internal sealed partial class McpServerImpl : McpServer
{
throw new McpProtocolException(
$"Tool '{tool.ProtocolTool.Name}' does not support task-augmented execution.",
McpErrorCode.MethodNotFound);
McpErrorCode.InvalidParams);
}
// Task augmentation requested - return CreateTaskResult
@ -604,7 +604,7 @@ internal sealed partial class McpServerImpl : McpServer
throw new McpProtocolException(
$"Tool '{tool.ProtocolTool.Name}' requires task-augmented execution. " +
"Include a 'task' parameter with the request.",
McpErrorCode.MethodNotFound);
McpErrorCode.InvalidParams);
}
// Normal synchronous execution