Results / truncation.structured-output-forced-tool
Structured output through a forced tool cut off at the token limit
A legacy forced structured_output tool stops at max_tokens with an incomplete input object.
Bug class: Truncation not reported as truncation
The provider stopped at the output token limit, but the library reports a normal finish, a generic parse error, or a partial result as success.
Agents accept partial output or retry without raising the limit, and structured pipelines ingest incomplete records.
Requirements
| Level | Id | Check | Requirement | Providers |
|---|---|---|---|---|
| MUST | no-partial-success | no_success_structured_value | A partial object is never returned as a successful result. | All |
| MUST | cause-is-truncation | truncation_is_signalled | The caller can tell that the output stopped at the token limit. | All |
| SHOULD | text-reported | text_matches_truth | The partial JSON text is available exactly as the provider sent it. | All |
| SHOULD | usage-reported | usage_matches_truth | Token usage is reported, and matches the provider's counts, even though the result is unusable. | All |
Fixtures
| Provider | Tier | any-llm | litellm | pydantic-ai | tanstack-ai | vercel-ai |
|---|---|---|---|---|---|---|
| anthropic | documented | – UNSUPPORTED | – UNSUPPORTED | ~ LOSSY | – UNSUPPORTED | – UNSUPPORTED |