Calendly API

39
Fair
Agent Native Score
Free TierAPI Key AuthOpenAPI Spec

Calendly's API enables programmatic access to scheduling, calendar management, and meeting automation. Agents can read/write events, manage availability, and integrate Calendly scheduling into workflows.

Categories: Scheduling · Calendar · Automation
#7 of 25 in Scheduling · #3 of 10 in Calendar · #20 of 99 in Automation
Checklist Breakdown

13 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 50%

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

Calendly has a well-documented OpenAPI spec and clear API documentation, making discovery solid. However, account creation requires human signup with no programmatic registration path—OAuth2 is the primary flow but requires initial human authorization. The API tooling is functional with good REST endpoints and structured JSON responses, though error messages could be more granular. Reliability is strong with good uptime reputation. The free tier limits API calls and event types, forcing paid tiers for production agent use. Main strength: established API with good docs; main weakness: OAuth-only auth model and account creation friction.

Top 10 Lists
Top 10 Scheduling → Top 10 Automation →

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claude mcp add --transport http agent-native-registry https://agentnativeregistry.com/api/mcp