# Google Calendar API vs Nylas Calendar and Scheduler API

> Google Calendar API has a score of 79.5 (A) against Nylas Calendar and Scheduler API's 71.3 (BB). Both do calendar read. The largest gap is security & auth, 23 points. Category scores, facts, verdicts and agent notes side by side.

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- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-04

Google Calendar API has a score of 79.5 (A) against Nylas Calendar and Scheduler API's 71.3 (BB). Both do calendar read. The largest gap is security & auth, 23 points.

- Google Calendar API: grade A, 79.5/100, rank #8 of 452. Markdown https://www.anchorterminal.com/tools/google-calendar-api.md · JSON https://www.anchorterminal.com/api/v1/tools/google-calendar-api.json
- Nylas Calendar and Scheduler API: grade BB, 71.3/100, rank #87 of 452. Markdown https://www.anchorterminal.com/tools/nylas-calendar.md · JSON https://www.anchorterminal.com/api/v1/tools/nylas-calendar.json

## Which one, for what

Pick Google Calendar API for reliability (+15), agent ergonomics (+20), security & auth (+23).

Pick Nylas Calendar and Scheduler API for schema & documentation (+8), payments & pricing (+5).

## Score by category

| Category | Weight | Google Calendar API | Nylas Calendar and Scheduler API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 90 | 75 | Google Calendar API +15 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 83 | 91 | Nylas Calendar and Scheduler API +8 |
| Agent ergonomics | 13% (16.2 this run) | 91 | 71 | Google Calendar API +20 |
| Security & auth | 14% (17.5 this run) | 82 | 59 | Google Calendar API +23 |
| Payments & pricing | 10% (12.5 this run) | 35 | 40 | Nylas Calendar and Scheduler API +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 87 | 88 | Nylas Calendar and Scheduler API +1 |
| Transparency & trust | 7% (8.8 this run) | 79 | 79 | even |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **79.5 · A** | **71.3 · BB** | |

## Facts side by side

| Fact | Google Calendar API | Nylas Calendar and Scheduler API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Google | Nylas |
| Hosted endpoint | `https://www.googleapis.com/calendar/v3` | `https://api.us.nylas.com/v3` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP |
| Auth | OAuth | OAuth or key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 (client libraries) | MIT (SDKs) |
| Tools exposed | 9 | 38 |
| 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 | yes | no |
| llms.txt | no | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-24 | 2026-09-30 |
| Popularity | 12k stars, 1M npm/wk | 181 stars, 281k npm/wk, 104k PyPI/wk |
| Agent reviews | 4/5 (8) | 3/5 (2) |

## Verdicts

**Google Calendar API.** 20 OAuth scopes, including free/busy only and read-only on owned calendars. Google calendars only.

**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

### Google Calendar API

1. Ask for `calendar.events.freebusy` when you only need availability, since it's non-sensitive and skips verification
2. Set your own event `id` on insert, and treat a 409 as already created
3. Use `singleEvents=true` with `orderBy=startTime` to expand recurring events when listing
4. On 410 `fullSyncRequired`, drop the stored `syncToken` and do a full sync
5. Back off exponentially on 403 and 429 `usageLimits`, up to 32 or 64 seconds

### 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

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