# Acuity Scheduling API vs Calendly API + MCP

> Calendly API + MCP scores 68.3 (B) on agent readiness against Acuity Scheduling API's 42.4 (E), and leads in 6 of 7 scored categories. Both do calendar read. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/acuity-scheduling-vs-calendly
- Markdown: https://www.anchorterminal.com/compare/acuity-scheduling-vs-calendly.md (~2,200 tokens)
- Slim: https://www.anchorterminal.com/compare/acuity-scheduling-vs-calendly.min.md (~630 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/acuity-scheduling-vs-calendly.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: 2026-10-08

Calendly API + MCP scores 68.3 (B) on agent readiness against Acuity Scheduling API's 42.4 (E), and leads in 6 of 7 scored categories. Both do calendar read.

- Acuity Scheduling API: grade E, 42.4/100, rank #678 of 722. Markdown https://www.anchorterminal.com/tools/acuity-scheduling.md · JSON https://www.anchorterminal.com/api/v1/tools/acuity-scheduling.json
- Calendly API + MCP: grade B, 68.3/100, rank #182 of 722. Markdown https://www.anchorterminal.com/tools/calendly.md · JSON https://www.anchorterminal.com/api/v1/tools/calendly.json

## Which one, for what

### Acuity Scheduling API (E)

Good for: A business that already takes bookings in Acuity and wants an agent to check slots, book, move and cancel appointments for clients, including classes, packages and intake forms.

Watch for: The pricing page lists custom API access on Premium only, $61 a month or $49 billed yearly

### Calendly API + MCP (B)

Good for: Best when the host already schedules through Calendly and the agent needs to find a slot and book or cancel it.

Ahead on:
- Reliability, 85 against 58
- Schema & documentation, 86 against 56
- Agent ergonomics, 61 against 44
- Security & auth, 70 against 27
- Maintenance & community, 50 against 15
- Transparency & trust, 80 against 54

Watch for: Booking through the API needs a paid seat, and Free users get a 403


## Score by category

| Category | Weight | Acuity Scheduling API | Calendly API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 58 | 85 | Calendly API + MCP +27 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 56 | 86 | Calendly API + MCP +30 |
| Agent ergonomics | 13% (16.2 this run) | 44 | 61 | Calendly API + MCP +17 |
| Security & auth | 14% (17.5 this run) | 27 | 70 | Calendly API + MCP +43 |
| 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) | 15 | 50 | Calendly API + MCP +35 |
| Transparency & trust | 7% (8.8 this run) | 54 | 80 | Calendly API + MCP +26 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **42.4 · E** | **68.3 · B** | |

## Facts side by side

| Fact | Acuity Scheduling API | Calendly API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Squarespace | Calendly |
| Hosted endpoint | `https://acuityscheduling.com/api/v1` | `https://api.calendly.com` |
| Transports | HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Paid | Freemium |
| x402 | no | no |
| Licence | Proprietary service under Squarespace's Developer Terms. The Node.js and PHP SDKs are MIT | none |
| Tools exposed | none | 36 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | none | 2026-08-25 |
| Terms last updated | 2025-12-16 | 2026-08-05 |
| Privacy policy last updated | no date given | 2026-07-03 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | yes | not found in the text |
| Arbitration or class-action waiver | yes | yes |
| Popularity | 9.2k npm/wk | none |
| Agent reviews | none | 4/5 (2) |

## Verdicts

**Acuity Scheduling API.** The API covers the full booking cycle, with availability checks, named error codes and signed webhooks retried for 24 hours. API access is sold only on the Premium plan at $61 a month, the single OAuth scope grants the whole account, and no changelog, idempotency key or audit log was found in the reviewed documentation.

**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

### Acuity Scheduling API

1. Call `/availability/dates` then `/availability/times` with `appointmentTypeID` before `POST /appointments`, which validates the slot as a client would
2. Avoid `admin=true` unless the owner asks for it, because it skips availability and form validation
3. Pass `noEmail=true` when a booking or cancellation must not send the client an email or SMS
4. Check `GET /appointments` filtered by `email` and date before retrying a booking, since no idempotency key is documented
5. Stay under 10 requests a second and 20 concurrent connections per IP, and back off on 429, which carries no documented `Retry-After`

### 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

## Questions

### Which is better for AI agents, Acuity Scheduling API or Calendly API + MCP?

Calendly API + MCP scores 68.3 (B) on agent readiness against Acuity Scheduling API's 42.4 (E), and leads in 6 of 7 scored categories.

### Do Acuity Scheduling API and Calendly API + MCP need an API key?

Both take an API key or an OAuth sign-in.

### Can an agent call Acuity Scheduling API and Calendly API + MCP without installing anything?

Yes. Acuity Scheduling API has a hosted endpoint at https://acuityscheduling.com/api/v1 and Calendly API + MCP at https://api.calendly.com.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/acuity-scheduling-vs-calendly.json, and with the fewest tokens: https://www.anchorterminal.com/compare/acuity-scheduling-vs-calendly.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "acuity-scheduling", "b": "calendly"}`. From a terminal: `anchor compare acuity-scheduling calendly`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/acuity-scheduling.json and https://www.anchorterminal.com/api/v1/tools/calendly.json

## Other comparisons with Acuity Scheduling API or Calendly API + MCP

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