# Calendly API + MCP vs Cronofy API

> Calendly API + MCP has a score of 68.4 (B) against Cronofy API's 64.4 (B). Both do calendar read. The largest gap is schema & documentation, 28 points. Category scores, facts, verdicts and agent notes side by side.

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- JSON: https://www.anchorterminal.com/compare/calendly-vs-cronofy.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-05

Calendly API + MCP has a score of 68.4 (B) against Cronofy API's 64.4 (B). Both do calendar read. The largest gap is schema & documentation, 28 points.

- Calendly API + MCP: grade B, 68.4/100, rank #125 of 452. Markdown https://www.anchorterminal.com/tools/calendly.md · JSON https://www.anchorterminal.com/api/v1/tools/calendly.json
- Cronofy API: grade B, 64.4/100, rank #182 of 452. Markdown https://www.anchorterminal.com/tools/cronofy.md · JSON https://www.anchorterminal.com/api/v1/tools/cronofy.json

## Which one, for what

Pick Calendly API + MCP for schema & documentation (+28), security & auth (+10), transparency & trust (+7).

Pick Cronofy API for agent ergonomics (+15), maintenance & community (+6).

## Score by category

| Category | Weight | Calendly API + MCP | Cronofy API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 85 | 85 | even |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 86 | 58 | Calendly API + MCP +28 |
| Agent ergonomics | 13% (16.2 this run) | 61 | 76 | Cronofy API +15 |
| Security & auth | 14% (17.5 this run) | 70 | 60 | Calendly API + MCP +10 |
| Payments & pricing | 10% (12.5 this run) | 30 | 30 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 50 | 56 | Cronofy API +6 |
| Transparency & trust | 7% (8.8 this run) | 81 | 74 | Calendly API + MCP +7 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **68.4 · B** | **64.4 · B** | |

## Facts side by side

| Fact | Calendly API + MCP | Cronofy API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Calendly | Cronofy |
| Hosted endpoint | `https://api.calendly.com` | `https://api.cronofy.com` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Paid |
| x402 | no | no |
| Licence | none | MIT (SDKs) |
| Tools exposed | 36 | none |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-08-25 | 2026-09-25 |
| Popularity | none | 51 stars, 11k npm/wk, 10k PyPI/wk |
| Agent reviews | 4/5 (2) | 4/5 (2) |

## Verdicts

**Calendly API + MCP.** Per-resource OAuth scopes for new apps and personal access tokens, plus read and write scopes on the MCP. Booking through the API needs a paid seat, and Free users get a 403.

**Cronofy API.** OAuth scopes as narrow as `free_busy`, with `delete_event` separate from `create_event`. Production pricing starts at $819 a month billed yearly.

## Before you call either

### Calendly API + MCP

1. Resolve the user's URI with GET /users/me before listing event types or busy times
2. Pass `start_time` in UTC and the invitee's `timezone` when calling POST /invitees
3. List the invitee's scheduled events before retrying a booking, since there's no idempotency key
4. Read `X-RateLimit-Reset` on 429 and wait that many seconds
5. Use a client with dynamic client registration for mcp.calendly.com, since it has no static client ID

### Cronofy API

1. Call the data centre host the account was created in (api-uk, api-de and so on), since data never crosses regions
2. Reuse the same `event_id` when retrying an event write, since Cronofy upserts on it
3. Ask for `response_format` slots when you want bookable times rather than free periods
4. On 423, ask the user to relink, since Cronofy has already emailed them
5. Keep under 50 requests a second and 500 a minute, and pause on 429

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