How to correctly use "Call n8n Workflow Tool" with an MCP Trigger-based workflow?

Questions
1

Describe the problem/error/question

I’m trying to set up a workflow that I can reuse as a Tool inside another workflow that uses the MCP Server Trigger. I want to pass inputs to this second workflow using the Call n8n Workflow Tool node.

The goal is to build an AI tool that generates and executes SQL queries (based on user instructions) via an LLM and returns a formatted CSV result — all inside the MCP framework.

I’ve set up the second workflow (the one to be called as a tool) with the MCP Trigger node, but I’m having trouble getting the inputs to pass correctly, and the execution doesn’t seem to trigger or return expected outputs.

What exactly needs to be modified in the workflow I want to call (the tool)?

  • Do I need to connect the MCP Trigger node to other nodes manually?
  • Is it correct to use {{$json.instruccion}} in the LLM prompt?
  • Do I need to return data from a specific node at the end for the output to be sent back?
  • Do I still need a Webhook node to do this?

Thanks!

Please share your workflow

Share the output returned by the last node

Information on your n8n setup

  • n8n version: 1.101.1
  • Database (default: SQLite):
  • n8n EXECUTIONS_PROCESS setting (default: own, main):
  • Running n8n via (Docker, npm, n8n cloud, desktop app): npm
  • Operating system: Windows
2

Hello @mark_serrano, welcome again to this community!
I will give you the example of how to call the MCP server from the AI, and you need to improve the AI Agent System prompt to make it understand how to use the mcp.

Hope it helps! And kindly mark my message as solution:)

1 Like
3

It looks like this workflow might work. I’m currently waiting for Claude’s services to return to normal so I can confirm whether it’s the right solution.

4

You can use Gemini too if you want ‘almost precise’ AI LLM.

5

It seems that with the trigger ‘when cat message received’ the workflow does not execute; the message from Claude is not connected to the activation of the workflow. It shows this error “Missing node to start execution”.

Workflows:

6

Hi, what is the correct process to use my own custom workflow in Claude via the MCP Server? It seems I may have missed a step or misconfigured something, as the workflow doesn’t trigger as expected when I try to use it from Claude.

7

I don’t know if it’s related or not, but in n8n version 1.102 and upper, claude and openai has a bug. But idk it will affect or not since you’re using groq node

8

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