Clerk

45
Fair
Agent Native Score
Free TierOpenAPI Spec

Authentication and user management. Drop-in UI components, JWT sessions, organizations, and a complete Backend API.

Categories: Auth
#3 of 6 in Auth
Checklist Breakdown

15 of 33 checks passed. 14 unscored.

Discovery 63%

Can an agent find and understand this tool without a web search?

Published OpenAPI/Swagger spec
Has llms.txt or llms-full.txt
Has an MCP server (official or well-maintained)
MCP server listed in a public registry
API reference docs are publicly accessible
Docs include runnable code examples
Has a public changelog or release notes
Has a public status page
Auth & Onboarding 83%

Can an agent create an account and get credentials without human intervention?

Signup does not require CAPTCHA
Signup does not require phone verification
Supports API key auth (not only OAuth)
API key obtainable without manual approval
No mandatory billing info to start
Can sign up without creating an organization
Pricing 100%

Can an agent operate autonomously without upfront payment or contracts?

Has a free tier
Usage-based pricing available
No minimum contract or commitment
Pricing page is public (no 'contact sales')
Free tier sufficient for testing (not just a trial)
Agent Tooling Not yet scored

How well does the API work for non-human consumers?

SDK available in 2+ languages
Structured error responses (JSON with error codes)
Idempotency support on write endpoints
Pagination on list endpoints
Webhook/event support
Sandbox or test mode available
Rate limit headers in responses
Consistent REST resource naming
Reliability Not yet scored

Does the tool fail gracefully when an agent makes a mistake?

Meaningful error messages (not just 500)
429 responses include Retry-After header
Documented uptime SLA (99.9%+)
Graceful degradation under rate limits
Request IDs in responses for debugging
API versioning supported
Reviewer Notes

Backend API is well-suited for agents managing users programmatically. Free tier up to 10,000 MAUs is generous. Good documentation. Better than Auth0 for agent use cases due to simpler Backend API.

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