Error “Execution id is missing” when using Gmail node with Send and Wait operation

[Vinodraj_Jayaraman]

I have a workflow where I send out a prompt from an MCP Client, and the flow looks like this:

[MCP Server Trigger] -> [Gmail Node (Send and Wait for Response)]

When the workflow executes, I receive the following error:

{
  "errorMessage": "Execution id is missing",
  "errorDetails": {},
  "n8nDetails": {
    "time": "19/9/2025, 11:49:35 am",
    "n8nVersion": "1.111.1 (Self Hosted)",
    "binaryDataMode": "default"
  }
}

Error Message

Execution id is missing

Information on your n8n setup

• n8n version: 1.111.1 (Self Hosted)

• Running n8n via: Docker

• Operating system: Linux Based

[emperial]

Hey @Vinodraj_Jayaraman

This error happens because the Gmail “Send and Wait for Response” node needs n8n to keep the workflow open with an execution id, which is something like a ticket number, but since your workflow starts from an MCP client, n8n doesn’t create that ticket, so when Gmail tries to wait it fails. The fix is to not use “Send and Wait”; instead, just send the email normally, and then use a Gmail Trigger node in another workflow to catch the reply and continue the process.

I hope this helps.

[Vinodraj_Jayaraman]

Thanks for the response, @emperial

The problem I want to solve is: We need to enable Decision Model and Notation (DMN) execution as part of our A2A integration with MCP through n8n.

Essentially, the challenge is: How can we achieve DMN workflows within our A2A MCP integration, given that n8n does not currently support this functionality?

The intended flow is:

• An A2A agent sends a request that triggers an email.

• When it reaches to n8n MCP Server Trigger, the gmail tool then send and wait for the recipient’s response.

• Once the user clicks “Approve” in the email, n8n should revert it back to the source agent and it should continue with the subsequent flow.

Thanks