Pain point · Reliability & bugs · Causes churn
MCP tool calls fail with new toolCallId and old workflows stop running after update
2 source threads · first seen 2025-11 · last seen 2025-11
Summary
After updating, MCP tool calls fail with a validation error about toolCallId, and in another workflow the agent shows running but never calls a model or tool.
- Affects
- n8n cloud users running MCP agents
Evidence
Excerpts are copied word for word from the source; follow the link to read it in full.
“MCP tool calls are failing due to new toolCallId, previous n8n worfklows won't run on update to most recent version!”
“the MCP Client Tool sends a `toolCallId`, which is not expected by my server”