fix(tasks): raise on failure so isError=true on the MCP wire#36
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sanjibani wants to merge 1 commit into
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fix(tasks): raise on failure so isError=true on the MCP wire#36sanjibani wants to merge 1 commit into
sanjibani wants to merge 1 commit into
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9 `except APIError as e: return _format_error(e)` and 9
`except Exception as e: return json.dumps({"error": True, ...})`
sites in apps/mcp-server/src/taskflow_mcp/tools/tasks.py all returned
JSON-encoded error strings. FastMCP wraps those as success content
with isError=false, so MCP clients treat the failure as data and the
LLM often proceeds as if the call had succeeded.
This is the same isError-compliance gap flagged in the recent MCP
security audit (Dayna Blackwell, 'Tool Poisoning, Rug Pulls, and
Prompt Injections — oh my!').
Each return is replaced with bare `raise` so the original exception
propagates and FastMCP sets isError=true on the wire while preserving
the formatted message in content for the LLM.
Regression test: apps/mcp-server/tests/test_iserror_compliance.py
asserts that a failing create_task call surfaces as ToolError
(isError=true on the wire).
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Summary
9
except APIError as e: return _format_error(e)and 9except Exception as e: return json.dumps({"error": True, ...})sites inapps/mcp-server/src/taskflow_mcp/tools/tasks.pyall returned JSON-encoded error strings. FastMCP wraps those as success content withisError=false, so MCP clients treat the failure as data and the LLM often proceeds as if the call had succeeded.This is the same
isError-compliance gap flagged in the recent MCP security audit (Dayna Blackwell, Tool Poisoning, Rug Pulls, and Prompt Injections — oh my!).Changes
Each return is replaced with bare
raiseso the original exception propagates and FastMCP setsisError=trueon the wire while preserving the formatted message incontentfor the LLM.Tests
apps/mcp-server/tests/test_iserror_compliance.pyasserts that a failingcreate_taskcall surfaces asToolError(isError=true on the wire).Reference: https://composio.dev/blog/mcp-security-vulnerabilities