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Sweep 31 Oct 2026 · 01:10Z Build v2.1.316 534 read Stable v2.1.309 Latest v2.1.316 Next v2.1.316 Feeds RSS JSON llms.txt llms-full.txt Unofficial
HomeDocsClaude Developer Platform 31 Oct 2026
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strict-tool-use changedagents-and-tools/tool-use/strict-tool-use

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33url: https://platform.claude.com/docs/en/agents-and-tools/tool-use/strict-tool-use
44description: Enforce JSON Schema compliance on Claude's tool inputs with grammar-constrained sampling.
55featureMetadata:
6 status: ga
6 status: stable
77 zdr:
88 eligibility: qualified
99 note: "Excludes [Covered Models](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#model-specific-data-retention-requirements). Your prompts and Claude's outputs are not stored. Only the JSON schema is cached, for up to 24 hours since last use. This also covers strict tool use (`strict: true` on tools), which uses the same grammar pipeline."
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2626 - claude-opus-4-5-20251101
2727 - claude-sonnet-4-5-20250929
2828 supportedPlatforms:
29 Claude API: ga
30 Claude Platform on AWS: ga
31 Amazon Bedrock: ga
32 Amazon Bedrock (InvokeModel): ga
33 Claude Models on Google Cloud (Google managed): ga
34 Microsoft Foundry: ga
29 Claude API: stable
30 Claude Platform on AWS: stable
31 Amazon Bedrock: stable
32 Amazon Bedrock (InvokeModel): stable
33 Claude Models on Google Cloud (Google managed): stable
34 Microsoft Foundry: stable
3535---
3636 
3737Setting `strict: true` on a tool definition guarantees Claude’s tool inputs match your JSON Schema by constraining the model’s token sampling to schema-valid outputs (a technique called grammar-constrained sampling). This page covers why strict mode matters for agents, how to enable it, and common use cases. For the supported JSON Schema subset, see [JSON Schema limitations](https://platform.claude.com/docs/en/build-with-claude/structured-outputs#json-schema-limitations). For non-strict schema guidance, see [Define tools](https://platform.claude.com/docs/en/agents-and-tools/tool-use/define-tools).
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