Symptom
After upgrading n8n, workflows that call tools through the MCP Client Tool node start failing.
Evidence what you'll see
- The error mentions toolCallId
- Workflows that ran before the upgrade now fail
- Happens with MCP servers that validate their input strictly
Cause
Agent metadata such as toolCallId was passed along as a tool argument, and strict MCP servers rejected the unexpected field.
Fix steps
0 of 1 done
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Verify the fix worked
- Run the workflow again and confirm the MCP tool call succeeds.
Sources and credit
Summarized in our own words from these public reports. Credit goes to their authors.
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