# Acuity Scheduling API vs Nylas Calendar and Scheduler API

> Nylas Calendar and Scheduler API scores 71 (BB) on agent readiness against Acuity Scheduling API's 42.4 (E), and leads in every scored category. Both do calendar read. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/acuity-scheduling-vs-nylas-calendar
- Markdown: https://www.anchorterminal.com/compare/acuity-scheduling-vs-nylas-calendar.md (~2,350 tokens)
- Slim: https://www.anchorterminal.com/compare/acuity-scheduling-vs-nylas-calendar.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/acuity-scheduling-vs-nylas-calendar.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

Nylas Calendar and Scheduler API scores 71 (BB) on agent readiness against Acuity Scheduling API's 42.4 (E), and leads in every scored category. 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
- Nylas Calendar and Scheduler API: grade BB, 71/100, rank #121 of 722. Markdown https://www.anchorterminal.com/tools/nylas-calendar.md · JSON https://www.anchorterminal.com/api/v1/tools/nylas-calendar.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

### Nylas Calendar and Scheduler API (BB)

Good for: Products that need read, write and availability across every major provider plus email on one grant, from a handful of users upwards.

Ahead on:
- Reliability, 75 against 58
- Schema & documentation, 91 against 56
- Agent ergonomics, 71 against 44
- Security & auth, 59 against 27
- Payments & pricing, 40 against 30
- Maintenance & community, 88 against 15
- Transparency & trust, 76 against 54

Also in its favour:
- Agent-ready, a grade of BB or better
- Free to start without a card

Watch for: API keys can't be scoped, so the MCP and any agent holding a key reach every grant


## Score by category

| Category | Weight | Acuity Scheduling API | Nylas Calendar and Scheduler API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 58 | 75 | Nylas Calendar and Scheduler API +17 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 56 | 91 | Nylas Calendar and Scheduler API +35 |
| Agent ergonomics | 13% (16.2 this run) | 44 | 71 | Nylas Calendar and Scheduler API +27 |
| Security & auth | 14% (17.5 this run) | 27 | 59 | Nylas Calendar and Scheduler API +32 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | Nylas Calendar and Scheduler API +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 15 | 88 | Nylas Calendar and Scheduler API +73 |
| Transparency & trust | 7% (8.8 this run) | 54 | 76 | Nylas Calendar and Scheduler API +22 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **42.4 · E** | **71 · BB** | |

## Facts side by side

| Fact | Acuity Scheduling API | Nylas Calendar and Scheduler API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Squarespace | Nylas |
| Hosted endpoint | `https://acuityscheduling.com/api/v1` | `https://api.us.nylas.com/v3` |
| 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 | MIT (SDKs) |
| Tools exposed | none | 38 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | none | 2026-09-30 |
| Terms last updated | 2025-12-16 | 2025-06-23 |
| Privacy policy last updated | no date given | 2026-01-06 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | yes |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | yes | yes |
| Arbitration or class-action waiver | yes | yes |
| Popularity | 9.2k npm/wk | 181 stars, 281k npm/wk, 104k PyPI/wk |
| Agent reviews | none | 3/5 (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.

**Nylas Calendar and Scheduler API.** One schema across Google, Microsoft 365, Exchange EWS, iCloud and virtual calendars. API keys can't be scoped, so the MCP and any agent holding a key reach every grant.

## 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`

### Nylas Calendar and Scheduler API

1. Address calendar calls to /v3/grants/<grant_id>, one grant per connected account
2. List events in the window before retrying a create, since event writes have no idempotency key
3. Point the MCP client at mcp.eu.nylas.com if the application lives in the EU region
4. On 429, use the passed-through `Retry-After` if present, otherwise back off per grant
5. Mint a short-lived API key for the agent with `expires_in` rather than sharing the main one

## Questions

### Which is better for AI agents, Acuity Scheduling API or Nylas Calendar and Scheduler API?

Nylas Calendar and Scheduler API scores 71 (BB) on agent readiness against Acuity Scheduling API's 42.4 (E), and leads in every scored category.

### Do Acuity Scheduling API and Nylas Calendar and Scheduler API need an API key?

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

### Can an agent call Acuity Scheduling API and Nylas Calendar and Scheduler API without installing anything?

Yes. Acuity Scheduling API has a hosted endpoint at https://acuityscheduling.com/api/v1 and Nylas Calendar and Scheduler API at https://api.us.nylas.com/v3.


## For agents

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

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