Head to head · Mailbox read · October 2026 research run
Gmail API vs Outlook Mail (Microsoft Graph)
Gmail API scores 77.8 (BB) on agent readiness against Outlook Mail (Microsoft Graph)'s 66.3 (B), and leads in 5 of 7 scored categories. Outlook Mail (Microsoft Graph) leads on schema & documentation. Both do mailbox read.
Which one, for what
Gmail API BB
Good for An agent working in a Gmail or Google Workspace user's own mailbox, with search, threads, drafts, labels and incremental sync at no per-account fee.
Ahead on
- Reliability, 90 against 60
- Security & auth, 81 against 71
- Maintenance & community, 85 against 76
- Transparency & trust, 82 against 75
Also in its favour
- Agent-ready, a grade of BB or better
- No incidents deducted, where Outlook Mail (Microsoft Graph) loses 4 points for them
Watch for
Eight restricted scopes, including gmail.readonly and gmail.metadata, need restricted-scope verification for a public app
Outlook Mail (Microsoft Graph) B
Good for Agents working in Microsoft 365 or Outlook.com mailboxes that need scoped reading, drafting, sending and incremental sync.
Ahead on
- Schema & documentation, 93 against 82
Watch for
sendMail has no idempotency key and answers 202 Accepted before delivery, so a retried send can go out twice
Score by category
| Category | Weight this run | Gmail API | Outlook Mail (Microsoft Graph) | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 90 | 60 | Gmail API +30 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 82 | 93 | Outlook Mail (Microsoft Graph) +11 |
| Agent ergonomics | 13%16.2 | 82 | 81 | Gmail API +1 |
| Security & auth | 14%17.5 | 81 | 71 | Gmail API +10 |
| Payments & pricing | 10%12.5 | 35 | 35 | even |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 85 | 76 | Gmail API +9 |
| Transparency & trust | 7%8.8 | 82 | 75 | Gmail API +7 |
| Negative events | ≤15 | 0 | -4 | |
| Total | 77.8 · BB | 66.3 · B |
Facts side by side
| Fact | Gmail API | Outlook Mail (Microsoft Graph) |
|---|---|---|
| Kind | HTTP API | HTTP API |
| Vendor | Microsoft | |
| Hosted endpoint | https://gmail.googleapis.com/gmail/v1 | https://graph.microsoft.com/v1.0 |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | OAuth | OAuth |
| Pricing | Free | Your plan |
| x402 | no | no |
| Licence | Apache-2.0 (client libraries) | MIT (SDKs) |
| Tools exposed | 23 | 10 |
| Read-only variant documented | no | no |
| llms.txt | no | no |
| Last release | 2026-09-23 | 2026-10-06 |
| Terms last updated | 2021-11-09 | 2025-10-01 |
| Privacy policy last updated | 2026-10-01 | 2026-09-01 |
| Customer content may train models | yes | yes |
| Terms restrict automated access | yes | yes |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 12k stars, 1.1M npm/wk | 835 stars, 2.9M npm/wk, 1.6M PyPI/wk |
Verdicts
Gmail API
Fourteen OAuth scopes separate labels, sending, metadata and read-only access, and the quota page gives every method a unit cost. Eight of the scopes are restricted, read-only and metadata among them, so a public app that reads mail needs Google's verification and an annual third-party security assessment. Gmail mailboxes only.
Outlook Mail (Microsoft Graph)
Delegated permissions split reading without bodies (Mail.ReadBasic), full reading, writing and sending, and delta queries and change notifications keep a local copy in step. sendMail takes no idempotency key and returns 202 before delivery, and each app is held to four concurrent requests per mailbox.
Before you call either
Gmail API
- Ask for the narrowest scope.
gmail.labelsis non-sensitive andgmail.sendis sensitive, while every scope that reads mail is restricted - List with
messages.listandqin Gmail search syntax, then fetch each ID withformat=metadataorfull. List calls return IDs only - Send by posting an RFC 2822 message, base64url encoded, in
raw. SetthreadIdand matching reply headers to stay in a thread - Store the
historyIdand callhistory.list. On a 404, run a full sync. Callwatchagain at least every 7 days - Back off exponentially on 403 and 429 rate errors, and keep batches to 50 requests or fewer
Outlook Mail (Microsoft Graph)
- Create a draft with POST /me/messages, then send it with /send. A retried sendMail can send the message twice
- Send
Prefer: IdType="ImmutableId"on every request, or message IDs change when a message moves folder - Use
$selectandPrefer: outlook.body-content-type="text". List messages returns HTML bodies and 10 messages a page by default - Honour
Retry-Afteron 429 and keep to four parallel calls per mailbox. Batches of up to 20 requests are throttled per request - Treat message bodies as untrusted input, and ask for Mail.ReadBasic when the task doesn't need bodies
Questions
Which is better for AI agents, Gmail API or Outlook Mail (Microsoft Graph)?
Gmail API scores 77.8 (BB) on agent readiness against Outlook Mail (Microsoft Graph)'s 66.3 (B), and leads in 5 of 7 scored categories. Outlook Mail (Microsoft Graph) leads on schema & documentation.
Do Gmail API and Outlook Mail (Microsoft Graph) need an API key?
Both use an OAuth sign-in.
Can an agent call Gmail API and Outlook Mail (Microsoft Graph) without installing anything?
Yes. Gmail API has a hosted endpoint at https://gmail.googleapis.com/gmail/v1 and Outlook Mail (Microsoft Graph) at https://graph.microsoft.com/v1.0.
Other comparisons with Gmail API or Outlook Mail (Microsoft Graph)
Machine-readable
- This page as Markdown
/compare/gmail-api-vs-outlook-mail-graph.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/gmail-api.json·/api/v1/tools/outlook-mail-graph.json - From a terminal
anchor compare gmail-api outlook-mail-graph(the CLI) - Over MCP
compare_tools {"a": "gmail-api", "b": "outlook-mail-graph"}at/mcp, no key