Why it matters

Without standard error handling, every agent integration reinvents retry logic. Getting the model right saves engineering everywhere.

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The architecture

Error format: standard fields (code, message, details, retryable flag).

HTTP status codes: 4xx client errors, 5xx server errors. Content includes structured A2A error.

A2A error categoriesClient error 4xxfix and retryServer error 5xxretry with backoffTask-level errorin task statusStructured errors include retryable flag; distinguish transient (retry) from permanent
Error taxonomy.
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How it works end to end

Task-level errors: task state becomes 'failed', error included in status.

Retryable errors: transient (rate limit, timeout). Backoff and retry.

Permanent errors: bad input, auth failure, capability missing. Don't retry.

Idempotency: task IDs enable safe retries. Server dedupes based on client-provided ID.