fix(server): allow tools with outputSchema to surface errors via unstructured content#2447
Open
SAY-5 wants to merge 2 commits intomodelcontextprotocol:v1.xfrom
Open
Conversation
…ructured content Per modelcontextprotocol#2429, a low-level tool with an `outputSchema` cannot return a tool-execution failure (e.g. "Resource not found") via unstructured `TextContent` because the call_tool decorator unconditionally validates the result against `outputSchema` and replaces the original error message with a hard "outputSchema defined but no structured output returned" error. Mirror the TypeScript SDK fix (modelcontextprotocol/typescript-sdk#655): when an outputSchema-bound tool returns no structured content, treat the unstructured payload as a tool-error result (`isError=True`) instead of replacing it. Tools that *do* return structured output keep their existing validation contract, and the explicit `CallToolResult`-returning path is unchanged. Github-Issue:modelcontextprotocol#2429
…w behavior CI flagged that the existing test_content_only_with_output_schema_error asserted the old contract (replace tool output with a generic 'outputSchema validation' message). This PR's whole point is to NOT do that, so the assertion was guaranteed to flip. Renames the test to test_content_only_with_output_schema_surfaces_error and updates assertions to verify the new contract: - isError = True (so callers can branch on it) - the tool's original unstructured TextContent payload is preserved verbatim (so callers see the tool's own error message, e.g. 'Resource not found', instead of a generic SDK validation string) - structuredContent stays None Verified locally with `python -m pytest tests/server/test_lowlevel_output_validation.py` → 9 passed. Signed-off-by: SAY-5 <say.apm35@gmail.com>
Author
|
Pushed 5239245 updating |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Per #2429, a low-level tool with an
outputSchemacannot return a tool-execution failure (e.g. "Resource not found") via unstructuredTextContentbecause thecall_tooldecorator unconditionally validates the result againstoutputSchemaand replaces the original error message with a hard "outputSchema defined but no structured output returned" error.This PR mirrors the TypeScript SDK fix in modelcontextprotocol/typescript-sdk#655: when an outputSchema-bound tool returns no structured content, treat the unstructured payload as a tool-error result (
isError=True) instead of replacing it. Tools that do return structured output keep their existing validation contract, and the explicitCallToolResult-returning path is unchanged.Closes #2429