Errors and retries

A failed tool call is not always safe to repeat. Decide what to do from the HTTP status and from whether a payment authorization was created or sent.

Status	Meaning	Recommended handling
400	Invalid tool input	Correct the body. Do not repeat it unchanged.
402	Payment required	Read the requirement, apply policy and authorize if approved.
404	Resource unavailable	Refresh discovery and select the current URL.
429	Capacity or rate limit	Use Retry-After or bounded backoff with jitter.
5xx	Gateway or tool failure	Check payment state before trying again.

After a paid request

Once an authorization has been sent, a timeout does not prove that settlement failed. Repeating the task with a new authorization can lead to duplicate spend. Reuse an idempotency key when supported and reconcile the earlier operation before creating another payment.