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401 Authorization header with Bearer token required

Your client reached the MCP endpoint without a Bearer token on the SSE connection. Fix:
  • send Authorization: Bearer YOUR_API_KEY
  • do not rely on a per-tool _apiKey argument

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401 invalid API key

The key was present but did not resolve to an active workspace credential. Fix:
  • verify the key value
  • verify the key is still active
  • verify you are using the right environment

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Your client cannot connect to /mcp

Some clients want the mounted server URL and some want the raw SSE path. Try both:
  • https://api.mailkatana.com/mcp
  • https://api.mailkatana.com/mcp/sse
If a direct request returns 401, the route exists and your client is still missing or dropping the Authorization header on the SSE connection. If the endpoint returns 404, treat that as a path or deployment problem instead.

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A tool you expected is not documented

Public MCP docs list the stable tool surface only. Some registered tools still return placeholder responses and are intentionally omitted until they return real workspace data.

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Tool returns An unexpected error occurred.

MailKatana sanitizes internal failures before returning them to MCP clients. If you see this message repeatedly:
  • retry the call once
  • verify the target object exists in the workspace
  • confirm your inputs match the documented tool arguments

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Requests start failing after bursts of traffic

The MCP mount shares the public developer rate limiter.
  • default limit: 600 requests per minute per IP
  • REST and MCP traffic count against the same developer-facing limiter