schemalint

Catch provider-incompatible schemas before OpenAI or Anthropic reject them at runtime.

OpenAI and Anthropic structured-output APIs accept only a strict subset of JSON Schema. Ship a schema with an unsupported keyword, a missing required entry, or the wrong additionalProperties, and the API rejects it — in production, at request time, as a 400.

schemalint catches those errors at build time, checked against the exact provider rules, so a bad schema fails your CI instead of your users' requests.

# npm / bun — adds the `schemalint` command to your project
npm install -D @1nder-labs/schemalint

# Rust
cargo install schemalint

# Python
pip install schemalint

Check a schema against OpenAI's structured-output rules:

schemalint check --profile openai.so.2026-04-30 schema.json

error[OAI-K-allOf]: keyword 'allOf' is not supported by openai.so.2026-04-30
  --> schema.json

1 issue found (1 error, 0 warnings) across 1 schema

Check a whole directory, for both providers at once:

schemalint check \
  --profile openai.so.2026-04-30 \
  --profile anthropic.so.2026-04-30 \
  schemas/

Schemas live in your code, not in .json files? schemalint reads them straight from your Zod or Pydantic definitions — no manual JSON Schema export, no second package to install.

// package.json
{
  "scripts": { "lint:schemas": "schemalint check-node" },
  "schemalint": {
    "profiles": ["openai.so.2026-04-30"],
    "include": ["src/**/*.ts"]
  }
}

npm run lint:schemas        # Zod  → check-node
schemalint check-python     # Pydantic → check-python

Exit 0 is a completeness guarantee: every discovered in-scope target was evaluated and checked, and no error diagnostic was produced. Import failures, schema-conversion failures, and partially checked batches exit 1. A run that discovers nothing (no matches) exits 3 and its human output starts with checked 0 schemas: nothing was discovered; --continue-on-discovery-error keeps collecting results but never converts partial coverage into success.

Machine-readable output uses schema version 1.1. Its additive report object contains coverage.status (complete, empty, partial, or failed), target counts, failures, and non-fatal warnings. Existing 1.0 fields retain their meaning.

The JSON-RPC server and ingestion caches are bounded and process-local. schemalint does not persist schemas or normalized schema data to disk.

• Unsupported keywords (allOf, oneOf, not, unsupported formats, …) per provider
• Missing required entries and additionalProperties: false mistakes
• Invalid root shapes, unsupported $ref patterns, and enum / nesting limits
• Size and depth limits that otherwise only surface as a runtime 400

schemalint exits non-zero on errors, so it fails the build before a broken schema ever ships:

- run: npx schemalint check --profile openai.so.2026-04-30 schemas/

Pick the output format that fits your pipeline:

schemalint check --format json   --profile openai.so.2026-04-30 schema.json   # machine-readable
schemalint check --format sarif  --profile openai.so.2026-04-30 schema.json   # code scanning
schemalint check --format gha    --profile openai.so.2026-04-30 schema.json   # GitHub Actions annotations

Coding agents (Claude Code, Codex, Cursor, ...) should start with the usage guide that ships inside the binary, so it always matches the installed version:

schemalint skills get core          # workflow, monorepo usage, exit codes, common fixes
schemalint skills get core --full   # plus the full command reference

• Installation · Quick start
• OpenAI profile · Anthropic profile
• Rule reference

Bug reports, new rules, and provider profiles are all welcome — see CONTRIBUTING.md and CODE_OF_CONDUCT.md.

Found a vulnerability? Please report it privately — see SECURITY.md.

Dual-licensed under MIT or Apache-2.0, at your option.