A fallback is an alternative action or implementation used when the preferred operation fails or exceeds its time budget. It keeps an agent useful instead of exposing an avoidable error. section 8.3.7
Treat failure as normal control flow: after a tool fails, an agent may retry, fall back, ask the user, or abandon the task. Limit retries so recovery does not become a runaway loop. section 1.1.3
Useful fallback choices include:
- Return a best-effort answer when the preferred tool cannot complete. section 8.3.7
- Switch to a smaller model when the primary model exceeds its budget or becomes unavailable. section 8.3.7
- Omit non-essential decoration, such as images, while preserving the core response. section 8.3.7
- Combine fallbacks with timeouts, budgets, circuit breakers, and graceful degradation to route around repeated or costly failures. section 8.3.7
Graceful alternatives
If text-to-speech is unavailable, continue with text. If an image tool is slow, return a link for viewing later. If confidence remains low or resources run out, present partial information, mark uncertainty, and suggest next steps. section 8.3.7 section 10.3.7
