docs: add file-tool error flow standardization design #455#456
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andrii-novikov wants to merge 1 commit into
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docs: add file-tool error flow standardization design #455#456andrii-novikov wants to merge 1 commit into
andrii-novikov wants to merge 1 commit into
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Internal file tools let raw DialExceptions escape their bodies, so the forward_tool_error_message flag introduced by #408 is a silent no-op for them: compose_tool_error_fallback_message forwards only ToolErrorException subclasses, which exist for MCP and REST tools but not for file tools. The LLM then reports vague failures like "the backend tool is failing" (#447). _download_text additionally mislabels Core 5xx errors as InvalidToolCallParameterException, telling the model to fix a parameter that is not broken and bypassing configured fallback strategies. The design standardizes every failure escaping a file tool into one of two shapes: InvalidToolCallParameterException for parameter-shaped failures (unchanged retry-with-a-fixed-value behavior) and a new FileToolErrorException(ToolErrorException) for genuine tool/server failures, plus forward_tool_error_message=True defaults for all nine file tool configs. Zero changes to the fallback machinery. Implementation is a follow-up; this PR carries only the design doc.
ypldan
approved these changes
Jul 17, 2026
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Applicable issues
ToolErrorExceptionsoforward_tool_error_messageworks for internal file tools #455 (design only — implementation is a follow-up PR, so the issue stays open)Description of changes
Adds the design doc
docs/designs/file_tool_error_flow.md(Status: Draft) for standardizing the internal file tools' error flow ontoToolErrorException.Why: #408 introduced
forward_tool_error_message, which forwards a tool's real error text to the LLM — but the gate incompose_tool_error_fallback_messageforwards onlyToolErrorExceptionsubclasses, and those exist for MCP and REST tools only. The internal file tools (dial_files_tooling/) let rawDialExceptions escape, so the flag is a silent no-op for them: the model receives only generic fallback instructions and reports vague failures like "the backend tool is failing" — the symptom of #447. On top of that,_download_textmislabels Core 5xx errors asInvalidToolCallParameterException, steering the model into "fix the parameter and retry" for a server fault and bypassing configured fallback strategies.The design: every failure escaping a file tool becomes one of exactly two standardized shapes —
InvalidToolCallParameterExceptionfor parameter-shaped failures (404/403/etag conflict/bad range — unchanged retry behavior) and a newFileToolErrorException(ToolErrorException)for genuine tool/server failures, produced by a translation helper in_base_file_tool.pythat replaces the 403-only_check_permission_denied. All nine file-tool configs shipforward_tool_error_message=Truedefaults. Zero changes to the fallback machinery; no schema changes (the file-tool configs are hardcoded, not manifest-driven).No implementation code in this PR — the doc will go through design review separately; implementation follows in its own PR.
Checklist
[ ] Changes are tested on review environment(docs-only change, nothing to deploy)[ ] App schema changes are backward compatible, or breaking changes are documented with a migration guide(no schema changes)[ ] Integration tests pass(docs-only change)By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.