Validate your APIs
before they break.
The only API linter that semantically understands your OpenAPI specifications. Built on academic research with 35+ rules, including 25+ citing peer-reviewed REST principles. Catch design issues regex can't see.
API quality, automated
Integrate REST Lens into your workflow and catch design issues early.
Semantic Understanding
Understands context, not just syntax. Knows 'status' is a valid endpoint, catches GET/POST tunneling. Goes beyond pattern matching.
Research-Backed Rules
35+ rules, including 25+ citing peer-reviewed studies (Bogner et al., Richardson & Ruby, Massé). Built on academic REST principles.
CI/CD Integration
Per-project API tokens for GitHub Actions, GitLab CI, Jenkins, or any pipeline. Enforce standards before merge.
Import Spectral Rulesets
Migrate from Spectral in minutes. Import existing YAML rulesets directly and benefit from semantic analysis.
Custom Rules in YAML
Create organization-specific rules with simple YAML syntax. No coding required. Enforce your standards across all projects.
Model Context Protocol
Integrate REST Lens via MCP into any compatible AI assistant. Evaluate APIs directly from your coding workflow.
API reviews on every PR.
Install the REST Lens GitHub App and get automatic API design reviews. No OpenAPI spec needed — reads your code, infers the API surface, and runs the same 35+ rules.
- Works with Express, FastAPI, Spring, Rails, and more
- Inline comments and check runs on your PR
- Uses your org's rules and custom rules
No OpenAPI spec? No problem.
REST Lens Capture is a reverse proxy sidecar that watches your live API traffic and infers an OpenAPI 3.1 spec automatically. Run it locally or as a Kubernetes sidecar.
Privacy-first: only types and shapes are stored, never raw values.
See it in action
We evaluated 3 well-known APIs. Browse the results, no signup required.
Twilio API
The leading cloud communications platform API, powering SMS, voice, and messaging for millions of developers.
Stripe API
The industry-standard payments API, used by millions of businesses worldwide.
GitHub REST API
The world's largest code hosting platform API, essential for developer tooling.
Why REST Lens?
See how we compare to other API validation tools
| Feature | REST Lens | Spectral | Postman | Stoplight |
|---|---|---|---|---|
| Semantic analysis | ||||
| Research-backed REST rules | Limited | Basic | ||
| Import Spectral rulesets | N/A | |||
| Custom rules (YAML) | Limited | |||
| Organization-level governance | Enterprise | Enterprise | ||
| Pricing model | €0.01/1K checks | Free / Self-host | $49-99/mo | $79-249/mo |
All tools have their strengths. REST Lens focuses on deep REST API quality with intelligent semantic analysis.
How it works
Get started in minutes, not hours.
Upload your spec
Upload your OpenAPI 3.x specification file or paste it directly.
Review results
See violations organized by severity with actionable recommendations.
Ship with confidence
Fix issues and integrate checks into your CI/CD pipeline.
Ready to improve your APIs?
Join teams using REST Lens to enforce API design standards.