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RestApiTool raises uncaught KeyError when a required path param is omitted #7282
Description
Description
FunctionTool returns {"error": ...} when mandatory args are missing so the model can retry.
RestApiTool maps filled args into path_params, then does self.endpoint.path.format(**path_params) in _prepare_request_params. An omitted required path parameter leaves a template key unset → KeyError (original OpenAPI name, e.g. 'userId').
RestApiTool.call only catches TimeoutException / HTTPStatusError, so the agent invocation aborts instead of returning a retryable tool error.
Location: google/adk/tools/openapi_tool/openapi_spec_parser/rest_api_tool.py
Environment
google-adk==2.9.2- Offline unit repro (no live HTTP)
Repro
# RestApiTool for path /users/{userId} with required path param userId / py_name user_id
# Call with args {} (or missing user_id)
# → KeyError: 'userId'Observed (google-adk==2.9.2)
- path
/users/{userId}, args{}→KeyError: 'userId' py_namesfor the param includeuser_id(declaration expects snake_case), but missing value still crashes viaformat
Expected
Missing required path params should return a structured tool error (mirror FunctionTool._get_mandatory_args) so the model can retry, not abort the agent run.
Suggested fix
Before format, verify every {placeholder} in the path is present; on miss return {"error": "missing path parameter …"}. Optionally catch KeyError/ValueError from _prepare_request_params in call.
Notes
Nearby RestApiTool crashes #7164 (header type) and #7206 (non-UTF-8 body) are different sites. Happy to open a PR.
Activity
chelsealong commentedon Sep 25, 2026
Picking this one up now — opening a PR shortly. Flagging it here so nobody duplicates the work; if someone is already on it, say so and I will drop mine.
michaelkillgta commentedon Sep 25, 2026
Thanks for picking this up so quickly — and for the PRs (#7285 / #7284 / #7283). Happy to review or clarify anything from the original repros if useful.
llalitkumarrr commentedon Sep 29, 2026
Hello @michaelkillgta,
We reproduced this issue in version 2.10.0, and it remains reproducible with this version as well. Furthermore we tested #7283 as well and it should resolve this issue. Could you please test it and provide your feedback?
michaelkillgta commentedon Sep 30, 2026
Looked at #7283. Catching the KeyError from
_prepare_request_paramsand returning a structured error matches the report, and the new test checks that the request is not sent and thatuserIdappears in the error.One caveat: any KeyError inside
_prepare_request_paramsis reported as a missing path parameter, even if the missing key is something else. Narrowing that to actual path params would be safer. I reviewed the diff only and have not run the suite.michaelkillgta commentedon Sep 30, 2026
Follow-up after running the tests. On #7283 (
74dda20),test_rest_api_tool.pypassed 100 tests, including the new missing-path-param case.The caveat is real. A required query param named
queryon/search?q={query}, supplied asquery=hello, returnsMissing required path parameter 'query'and never makes the HTTP call. AKeyErrorraised from_default_headersis reported the same way.fix: return structured error when RestApiTool is missing required pat…