Spectral
Open-source API description linter for OpenAPI (2.0, 3.0, 3.1), AsyncAPI, and custom JSON/YAML documents. Spectral validates API specs against ruleset files — built-in rulesets for OpenAPI best practices, or custom rules for organization-specific API standards. Integrates with CI to enforce API design standards across teams. Created by Stoplight, the API design platform.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Local execution only. Apache 2.0 licensed. Linting API specs reduces security risks by enforcing proper auth documentation and schema validation standards.
⚡ Reliability
Best When
You want to enforce API design standards across teams by linting OpenAPI specs in CI — Spectral is the de facto standard for OpenAPI linting.
Avoid When
You need runtime API validation or code generation — Spectral only validates API description documents.
Use Cases
- • Lint OpenAPI specifications in CI pipelines to catch design issues before they reach production — missing descriptions, invalid schemas, incorrect patterns
- • Enforce organization-specific API design standards with custom Spectral rulesets — naming conventions, required fields, forbidden patterns
- • Validate AsyncAPI specifications for event-driven API documentation quality
- • Integrate OpenAPI validation into agent API generation pipelines to ensure generated specs meet quality standards
- • Share API design rules across teams via versioned Spectral ruleset packages published to npm
Not For
- • Runtime API validation — Spectral validates API description documents, not live API responses
- • Code generation from OpenAPI — use openapi-generator or openapi-typescript for code generation
- • Full API testing — use Postman, Hoppscotch, or API testing tools for behavioral tests
Interface
Authentication
No authentication — local linting tool. Stoplight Platform (commercial) adds team collaboration features.
Pricing
Apache 2.0 licensed open source core. Stoplight Platform adds managed rulesets, collaboration, and reporting.
Agent Metadata
Known Gotchas
- ⚠ Custom rulesets must be published or referenced by path — using npm-published rulesets requires internet access in CI; cache node_modules for offline CI
- ⚠ Spectral resolves $ref references during linting — circular $ref patterns or unresolvable external refs cause linting to fail before rule evaluation
- ⚠ Rule severity levels (error, warn, hint, info) affect exit code — only 'error' severity causes non-zero exit; configure severity appropriately for CI blocking
- ⚠ OpenAPI 3.1 support added in Spectral 6 — older rulesets or plugins may not correctly handle 3.1-specific features like webhooks or nullable changes
- ⚠ Large OpenAPI files (1000+ paths) can be slow to lint — Spectral processes the entire document in memory; split large specs or optimize rule set for performance
- ⚠ Extending built-in rulesets requires proper 'extends' syntax — 'spectral:oas' extends the OAS rules; incorrect extends causes rules to not apply
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Spectral.
Scores are editorial opinions as of 2026-03-06.