Anthropic Tool Schema Validator
Check Anthropic tool definitions, ordinary tool syntax, and strict tool schema limits.
Tool or input schema
Paste one JSON or YAML tool definition or raw Draft 2020-12 schema. Analysis runs in your browser.
Contract inputAnalysis results
Ready to analyze
Load an example or paste one tool definition, then choose Analyze locally.
Rules checked against
Anthropic strict tool · rule pack 1.0.0 · last verified 2026-10-07
What this checks
Anthropic strict tool use permits optional properties within documented request limits, but has its own constraints on references, numeric and string limits, regex, and arrays. The ordinary tool mode is separate from strict mode.
Base schema and provider rules
Base JSON Schema Draft 2020-12 validity, wrapper validity, and provider compatibility are separate results. Undeclared schemas are explicitly treated as Draft 2020-12. External references are not fetched.
Repairs, conversion, and privacy
Only selected deterministic changes are previewed. Closing objects changes accepted values. Optional-to-required changes are never automatic. Conversion preserves the original until you choose Apply. Input and previews remain in this browser session; no provider APIs, keys, server validation, or automatic persistence are used.
Sources and limits
The selected mode displays its official documentation, rule pack version, and verification date in the results. A missing or undocumented provider rule stays uncertain. Each input is limited to 256 KiB; analysis stops after ten seconds.