Symptom
MCP tools such as write_file receive a parsed object for a string parameter (like file content that is JSON), so the call fails or writes the wrong content.
Evidence what you'll see
- The parameter is declared as type string in the tool's input schema
- The value arrives as an object instead of the JSON text
- Built-in tools are not affected
Cause
Tool arguments were deep-parsed with JSON.parse, and MCP tools had no step that turned values back into strings to match their schema.
Fix steps
0 of 1 done
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Verify the fix worked
- Ask the agent to write a JSON file through an MCP file tool and confirm the file contains the JSON text.
Sources and credit
Summarized in our own words from these public reports. Credit goes to their authors.
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