Your agent calls a tool, the tool calls a slow external service, and it takes 30 seconds or never answers. The agent waits, then dies with a cryptic error. One slow dependency took down the whole run. The fix is an async call: if a tool can be slow, do not wait on it. One tool starts the work and hands back a tracking id right away, another checks if it is done. The agent stays responsive and polls for the result. That turns a 300 second hang into about a 4 second response, and timeouts and cleanup keep stalled jobs from piling up.

What you'll learn: • Apply a simple rule to classify any tool call as safe to block or required to go asynchronous • Build the async handle pattern: one tool returns a tracking id instantly, another polls for the result • Design job lifecycle and cleanup so completed and stalled jobs do not leak memory • Implement clear error and timeout states so failed dependencies surface instead of hanging • Evaluate polling against callback delivery and choose per use case Outline: • One slow dependency, whole workflow down • The pattern is older than agents • Build the async boundary • Make it production safe • The decision checklist