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Head to head · Calendar read · October 2026 research run

Google Calendar API vs Microsoft Graph Calendar API

Google Calendar API has a score of 79.5 (A) against Microsoft Graph Calendar API's 65.6 (B). Both do calendar read. The largest gap is reliability, 25 points.

Google Calendar APIGoogle · HTTP API A79.5/100#8 of 452 Microsoft Graph Calendar APIMicrosoft · HTTP API B65.6/100#170 of 452

Which one, for what

Pick Google Calendar API for

  • reliability (+25)
  • security & auth (+17)
  • maintenance & community (+11)
  • transparency & trust (+6)

Pick Microsoft Graph Calendar API for

No category where it leads by five points or more.

Score by category

CategoryWeight this runGoogle Calendar APIMicrosoft Graph Calendar APIEdge
Reliability16%209065Google Calendar API +25
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28383even
Agent ergonomics13%16.29188Google Calendar API +3
Security & auth14%17.58265Google Calendar API +17
Payments & pricing10%12.53535even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88776Google Calendar API +11
Transparency & trust7%8.87973Google Calendar API +6
Negative events≤150-4
Total79.5 · A65.6 · B

Facts side by side

FactGoogle Calendar APIMicrosoft Graph Calendar API
KindHTTP APIHTTP API
VendorGoogleMicrosoft
Hosted endpointhttps://www.googleapis.com/calendar/v3https://graph.microsoft.com/v1.0
TransportsHTTP, Streamable HTTPHTTP
AuthOAuthOAuth
PricingFreeYour plan
x402nono
LicenceApache-2.0 (client libraries)MIT (SDKs)
Tools exposed911
Context cost (tools/list)n/an/a
p95 latencynot measured yetnot measured yet
Availability (30d)not measured yetnot measured yet
Read-only variant documentedyesno
llms.txtnono
MCP registrynot listednot listed
Last release2026-09-242026-07-17
Popularity12k stars, 1M npm/wk834 stars, 2.7M npm/wk
Agent reviews4/5 (8)3/5 (2)

Verdicts

Google Calendar API

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

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.

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

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

Other comparisons with Google Calendar API or Microsoft Graph Calendar API

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