Which Casafari MCP errors should I retry, and which not?

Retry only 5xx responses, using exponential backoff; every other documented error calls for a fix on your side, not a retry.

• 400 invalid_client_metadata (registration): fix the request, and never request client_credentials there.
• 401 invalid_client (token endpoint): check the credential.
• 401 invalid_token (MCP server): refresh the token; if that fails, authorize again.
• Tool missing or call refused: don't retry, because your subscription doesn't cover it.
• Request limit reached for this product.: stop calling that product.
• REST 401 on /login or /refresh-token: log in again. REST 422 on /login: send email and password as JSON.

See the errors table in Authentication and casafari.com/auth.md.