MCP workflow execution via Claude Desktop creates queued executions with no input data

[Cameron_Mulvey]

I’m trying to execute an n8n workflow via the MCP integration from Claude (claude.ai).

The workflow is marked as “Available in MCP” and Claude can successfully:

• Search for workflows (search_workflows works)

• Get workflow details (get_workflow_details works)

However, when Claude attempts to execute the workflow using execute_workflow, the following happens:

1. Claude receives an immediate error: "Unknown execution mode"

2. An execution IS created in n8n and appears in the queue as “Starting soon”

3. The execution remains stuck in queue indefinitely

4. No input data is passed to the workflow — the trigger node shows no input/message

Workflow Setup:

The workflow has multiple triggers connected to an AI Agent node:

• Chat Trigger (primary)

• Webhook Trigger (POST)

• Form Trigger

All triggers are connected to the same AI Agent that uses an MCP Client to call Apify scrapers.

What I’ve Tried:

1. Executing with type: "chat" and chatInput parameter

2. Executing with type: "form" and formData parameter

3. Executing with type: "webhook" and webhookData parameter

4. Switching webhook from GET to POST

5. Adding a Form Trigger with defined fields

All attempts result in the same behavior: “Unknown execution mode” error returned to Claude, execution queued in n8n with no input data.

Expected Behavior:

The workflow should execute with the provided input data (e.g., a TikTok URL to scrape) and return the result to Claude.

Execution Attempts:

Claude’s MCP tool attempts with various input formats all return the same error:

{"success":false,"executionId":null,"error":"Unknown execution mode"}

Despite the error, executions appear in n8n’s queue — but with no input data, causing them to hang.

Questions:

1. Is there a specific input format required for MCP execution via Claude Desktop Connectors? In the release video, it said form, chat, and webhook should all work.

2. The video mentions “native connection into all of the most popular chat apps” is coming — is Claude Desktop Connectors the right method currently, or should we wait for native integration?

3. Why would executions queue with no input data when the MCP call includes input parameters?

4. Is there documentation on the expected payload format for execute_workflow?

[Parintele_Damaskin]

@Cameron_Mulvey

The workflow has multiple triggers connected to an AI Agent node:

• Chat Trigger (primary)
• Webhook Trigger (POST)
• Form Trigger

All triggers are connected to the same AI

Hey @Cameron_Mulvey !

I think you have to use only one Trigger per workflow based on the docs:

Accessing n8n MCP server | n8n Docs

[Cameron_Mulvey]

Thanks - I tried only one with Chat, but based on feedback from others it seems like Webhooks are the only way to do this. I did get it functional with Webhooks.