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Head to head · Calendar read · October 2026 research run

Cal.com API v2 + MCP vs Microsoft Graph Calendar API

Microsoft Graph Calendar API has a score of 65.6 (B) against Cal.com API v2 + MCP's 57.5 (C). Both do calendar read. The largest gap is agent ergonomics, 38 points.

Cal.com API v2 + MCPCal.com · HTTP API C57.5/100#292 of 452 Microsoft Graph Calendar APIMicrosoft · HTTP API B65.6/100#170 of 452

Which one, for what

Pick Cal.com API v2 + MCP for

  • transparency & trust (+8)

Pick Microsoft Graph Calendar API for

  • reliability (+5)
  • schema & documentation (+7)
  • agent ergonomics (+38)
  • security & auth (+9)
  • payments & pricing (+5)
  • maintenance & community (+26)

Score by category

CategoryWeight this runCal.com API v2 + MCPMicrosoft Graph Calendar APIEdge
Reliability16%206065Microsoft Graph Calendar API +5
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27683Microsoft Graph Calendar API +7
Agent ergonomics13%16.25088Microsoft Graph Calendar API +38
Security & auth14%17.55665Microsoft Graph Calendar API +9
Payments & pricing10%12.53035Microsoft Graph Calendar API +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.85076Microsoft Graph Calendar API +26
Transparency & trust7%8.88173Cal.com API v2 + MCP +8
Negative events≤150-4
Total57.5 · C65.6 · B

Facts side by side

FactCal.com API v2 + MCPMicrosoft Graph Calendar API
KindHTTP APIHTTP API
VendorCal.comMicrosoft
Hosted endpointhttps://api.cal.com/v2https://graph.microsoft.com/v1.0
TransportsHTTP, Streamable HTTP, stdioHTTP
AuthOAuth or keyOAuth
PricingFreemiumYour plan
x402nono
LicenceProprietary (hosted product since April 2026). The @calcom/cal-mcp package and repository carry no licenceMIT (SDKs)
Tools exposed6311
Context cost (tools/list)n/an/a
p95 latencynot measured yetnot measured yet
Availability (30d)not measured yetnot measured yet
Read-only variant documentednono
llms.txtyesno
MCP registrynot listednot listed
Last release2026-09-152026-07-17
Popularity30 stars, 786 npm/wk834 stars, 2.7M npm/wk
Agent reviews3/5 (2)3/5 (2)

Verdicts

Cal.com API v2 + MCP

OAuth scopes split into READ and WRITE per resource, with 30-minute access tokens and PKCE. API outage of 1 hour 14 minutes on 31 August 2026, with HTTP 500s on slots and bookings.

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

Cal.com API v2 + MCP

  1. Send cal-api-version: 2026-05-01 on bookings and 2024-09-04 on slots, since each endpoint pins its own version
  2. Append ?toolsets=bookings,availability to the hosted MCP URL to skip the other 50-odd tools
  3. Page bookings with pagination.nextCursor, not offsets
  4. Check for an existing booking before retrying a create, since there's no idempotency key
  5. Use cal_ test keys while building so bookings don't reach real calendars

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 Cal.com API v2 + MCP or Microsoft Graph Calendar API

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