# Cal.com API v2 + MCP vs Calendly API + MCP

> Calendly API + MCP has a score of 68.4 (B) against Cal.com API v2 + MCP's 57.5 (C). Both do calendar read. The largest gap is reliability, 25 points. Category scores, facts, verdicts and agent notes side by side.

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- 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 Cal.com API v2 + MCP's 57.5 (C). Both do calendar read. The largest gap is reliability, 25 points.

- Cal.com API v2 + MCP: grade C, 57.5/100, rank #292 of 452. Markdown https://www.anchorterminal.com/tools/cal-com.md · JSON https://www.anchorterminal.com/api/v1/tools/cal-com.json
- 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

## Which one, for what

Pick Cal.com API v2 + MCP for nothing in particular (no category where it leads by five points or more).

Pick Calendly API + MCP for reliability (+25), schema & documentation (+10), agent ergonomics (+11), security & auth (+14).

## Score by category

| Category | Weight | Cal.com API v2 + MCP | Calendly API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 85 | Calendly API + MCP +25 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 76 | 86 | Calendly API + MCP +10 |
| Agent ergonomics | 13% (16.2 this run) | 50 | 61 | Calendly API + MCP +11 |
| Security & auth | 14% (17.5 this run) | 56 | 70 | Calendly API + MCP +14 |
| 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 | 50 | even |
| Transparency & trust | 7% (8.8 this run) | 81 | 81 | even |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.5 · C** | **68.4 · B** | |

## Facts side by side

| Fact | Cal.com API v2 + MCP | Calendly API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Cal.com | Calendly |
| Hosted endpoint | `https://api.cal.com/v2` | `https://api.calendly.com` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Proprietary (hosted product since April 2026). The @calcom/cal-mcp package and repository carry no licence | none |
| Tools exposed | 63 | 36 |
| 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 | 2026-09-15 | 2026-08-25 |
| Popularity | 30 stars, 786 npm/wk | none |
| Agent reviews | 3/5 (2) | 4/5 (2) |

## Verdicts

**Cal.com API v2 + MCP.** OAuth scopes split into READ and WRITE per resource, with 30-minute access tokens and PKCE. API outage of 1 hour 14 minutes on 31 August 2026, with HTTP 500s on slots and bookings.

**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.

## Before you call either

### Cal.com API v2 + MCP

1. Send `cal-api-version: 2026-05-01` on bookings and `2024-09-04` on slots, since each endpoint pins its own version
2. Append `?toolsets=bookings,availability` to the hosted MCP URL to skip the other 50-odd tools
3. Page bookings with `pagination.nextCursor`, not offsets
4. Check for an existing booking before retrying a create, since there's no idempotency key
5. Use `cal_` test keys while building so bookings don't reach real calendars

### 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

## Other comparisons with Cal.com API v2 + MCP or Calendly API + MCP

- [Apiroc Unified Calendar API vs Cal.com API v2 + MCP](https://www.anchorterminal.com/compare/apiroc-vs-cal-com.md)
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