# Microsoft Graph Calendar API vs Nylas Calendar and Scheduler API

> Nylas Calendar and Scheduler API has a score of 71.3 (BB) against Microsoft Graph Calendar API's 65.6 (B). Both do calendar read. The largest gap is agent ergonomics, 17 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

Nylas Calendar and Scheduler API has a score of 71.3 (BB) against Microsoft Graph Calendar API's 65.6 (B). Both do calendar read. The largest gap is agent ergonomics, 17 points.

- Microsoft Graph Calendar API: grade B, 65.6/100, rank #170 of 452. Markdown https://www.anchorterminal.com/tools/microsoft-graph-calendar.md · JSON https://www.anchorterminal.com/api/v1/tools/microsoft-graph-calendar.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 Microsoft Graph Calendar API for agent ergonomics (+17), security & auth (+6).

Pick Nylas Calendar and Scheduler API for reliability (+10), schema & documentation (+8), payments & pricing (+5), maintenance & community (+12), transparency & trust (+6).

## Score by category

| Category | Weight | Microsoft Graph Calendar API | Nylas Calendar and Scheduler API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 65 | 75 | Nylas Calendar and Scheduler API +10 |
| 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) | 88 | 71 | Microsoft Graph Calendar API +17 |
| Security & auth | 14% (17.5 this run) | 65 | 59 | Microsoft Graph Calendar API +6 |
| 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) | 76 | 88 | Nylas Calendar and Scheduler API +12 |
| Transparency & trust | 7% (8.8 this run) | 73 | 79 | Nylas Calendar and Scheduler API +6 |
| Negative events | ≤15 | -4 | 0 | |
| **Total** | | **65.6 · B** | **71.3 · BB** | |

## Facts side by side

| Fact | Microsoft Graph Calendar API | Nylas Calendar and Scheduler API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Microsoft | Nylas |
| Hosted endpoint | `https://graph.microsoft.com/v1.0` | `https://api.us.nylas.com/v3` |
| Transports | HTTP | HTTP, Streamable HTTP |
| Auth | OAuth | OAuth or key |
| Pricing | Your plan | Freemium |
| x402 | no | no |
| Licence | MIT (SDKs) | MIT (SDKs) |
| Tools exposed | 11 | 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 | no | no |
| llms.txt | no | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-07-17 | 2026-09-30 |
| Popularity | 834 stars, 2.7M npm/wk | 181 stars, 281k npm/wk, 104k PyPI/wk |
| Agent reviews | 3/5 (2) | 3/5 (2) |

## Verdicts

**Microsoft Graph Calendar API.** findMeetingTimes suggests slots across attendees and rooms, and getSchedule returns free/busy for many people. 4 concurrent requests per app per mailbox.

**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

### Microsoft Graph Calendar API

1. Send `Prefer: outlook.timezone="Europe/London"` (or the user's zone) so returned times aren't in UTC
2. Set a `transactionId` on event creates so a retry doesn't double-book
3. Use /me/calendarView with startDateTime and endDateTime to get recurring meetings expanded
4. Honour `Retry-After` on 429 and keep to 4 parallel calls per mailbox
5. Ask for Calendars.ReadBasic when you don't need event bodies

### 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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