n8n MCP Tool Using Wrong Authentication Header

[mlanzlot]

Issue: The n8n MCP tool is using Authorization: Bearer header instead of the required X-N8N-API-KEY header when making API calls to n8n instances.
Expected Behavior:
API calls should use X-N8N-API-KEY: YOUR_API_KEY header
This is the standard header format for n8n API authentication
Actual Behavior:
MCP tool uses Authorization: Bearer YOUR_API_KEY header
Results in authentication errors: {"message":"'X-N8N-API-KEY' header required"}
Environment:
n8n MCP tool version: 2.11.2
n8n instance: n8n.cloud (https://lanzko.app.n8n.cloud/)
MCP configuration: Correct (API key and URL are properly set)
Reproduction Steps:
Configure n8n MCP with valid API key and URL
Try to list workflows: n8n_list_workflows()
Get authentication error despite correct configuration
Same API key works fine with direct curl: curl -H "X-N8N-API-KEY: KEY" "https://instance.com/api/v1/workflows"
Workaround:
Currently using direct curl commands instead of MCP tools for n8n API operations.
Request:
Please update the MCP tool to use the correct X-N8N-API-KEY header format for n8n API authentication.

[ashleybarrett1979]

Additional Header Issue Found

I'm experiencing a similar but different authentication header issue:

My Environment:

• Self-hosted n8n: https://n8n.srv845860.hstgr.cloud
• n8n-mcp version: latest (npx n8n-mcp)

My Issue:
Missing Accept: application/json header causes authentication failure

Evidence:
✅ Works: curl -H "X-N8N-API-KEY: key" -H "Accept: application/json" URL
❌ Fails: curl -H "X-N8N-API-KEY: key" URL → {"message":"unauthorized"}

Summary:
Different n8n instances require different header combinations:

• n8n.cloud: needs X-N8N-API-KEY header (not Bearer)
• Self-hosted: needs BOTH X-N8N-API-KEY AND Accept: application/json

The n8n-mcp tool needs to support both header requirements.