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HomeDocsModel Context Protocol 29 Jul 2026
One change · mcp

SEP-1303: Input Validation Errors as Tool Execution Errors changedseps/1303-input-validation-errors-as-tool-execution-errors

Upstream edited this page at 29 Jul 2026 22:46 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 22 Oct 2026 20:37 UTC.

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1111> This SEP has reached Final status and is preserved as a historical record of
1212> the design as accepted. Changes made to the protocol after finalization are
1313> not reflected here. Refer to the [current
14> specification](/specification/latest) and its changelog for authoritative
14> specification](/specification/latest.md) and its changelog for authoritative
1515> requirements.
1616 
1717| Field | Value |
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7676 
7777### Current Behavior
7878 
79The [tool errors specification](https://modelcontextprotocol.io/specification/2025-06-18/server/tools#error-handling) currently provides ambiguous guidance:
79The [tool errors specification](https://modelcontextprotocol.io/specification/2025-06-18/server/tools.md#error-handling) currently provides ambiguous guidance:
8080 
8181* "Invalid arguments" should be treated as Protocol Error
8282* "Invalid input data" should be treated as Tool Execution Error
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194194 
195195## References
196196 
197* [MCP Tools Error Handling Specification](https://modelcontextprotocol.io/specification/2025-06-18/server/tools#error-handling)
197* [MCP Tools Error Handling Specification](https://modelcontextprotocol.io/specification/2025-06-18/server/tools.md#error-handling)
198198* [Better MCP tools/call Error Responses: Help Your AI Recover Gracefully](https://dev.to/alpic/better-mcp-toolscall-error-responses-help-your-ai-recover-gracefully-15c7)
199199* Related Issue: [https://github.com/modelcontextprotocol/typescript-sdk/pull/824](https://github.com/modelcontextprotocol/typescript-sdk/pull/824)
200200 
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