# Fastmail API (JMAP) vs Gmail API > Gmail API scores 77.8 (BB) on agent readiness against Fastmail API (JMAP)'s 54.1 (C), and leads in every scored category. Both do mailbox read. Category scores, facts, verdicts and agent notes side by side. - Canonical: https://www.anchorterminal.com/compare/fastmail-vs-gmail-api - Markdown: https://www.anchorterminal.com/compare/fastmail-vs-gmail-api.md (~2,200 tokens) - Slim: https://www.anchorterminal.com/compare/fastmail-vs-gmail-api.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts) - JSON: https://www.anchorterminal.com/compare/fastmail-vs-gmail-api.json (this page as data, same URL with Accept: application/json) - Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt) - API: https://www.anchorterminal.com/api/v1/index.json - Updated: 2026-10-09 Gmail API scores 77.8 (BB) on agent readiness against Fastmail API (JMAP)'s 54.1 (C), and leads in every scored category. Both do mailbox read. - Fastmail API (JMAP): grade C, 54.1/100, rank #620 of 842. Markdown https://www.anchorterminal.com/tools/fastmail.md · JSON https://www.anchorterminal.com/api/v1/tools/fastmail.json - Gmail API: grade BB, 77.8/100, rank #18 of 842. Markdown https://www.anchorterminal.com/tools/gmail-api.md · JSON https://www.anchorterminal.com/api/v1/tools/gmail-api.json ## Which one, for what ### Fastmail API (JMAP) (C) Good for: An agent working in its owner's own Fastmail mailbox, where JMAP gives batched reads, structured search and state-based sync on an open standard, and MCP gives a ready connection with read, write and send levels. Watch for: The customer terms forbid programmatically generated email to addresses outside the account, and say the service is not for machine-to-machine workflows ### 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 54 - Schema & documentation, 82 against 52 - Agent ergonomics, 82 against 73 - Security & auth, 81 against 60 - Payments & pricing, 35 against 30 - Maintenance & community, 85 against 26 - Transparency & trust, 82 against 74 Also in its favour: - Agent-ready, a grade of BB or better - A hosted endpoint, with nothing to install Watch for: Eight restricted scopes, including `gmail.readonly` and `gmail.metadata`, need restricted-scope verification for a public app ## Score by category | Category | Weight | Fastmail API (JMAP) | Gmail API | Edge | | --- | --- | --- | --- | --- | | Reliability | 16% (20 this run) | 54 | 90 | Gmail API +36 | | Performance | 10%, pending | pending | pending | not scored in this run | | Schema & documentation | 13% (16.2 this run) | 52 | 82 | Gmail API +30 | | Agent ergonomics | 13% (16.2 this run) | 73 | 82 | Gmail API +9 | | Security & auth | 14% (17.5 this run) | 60 | 81 | Gmail API +21 | | Payments & pricing | 10% (12.5 this run) | 30 | 35 | Gmail API +5 | | Task success | 10%, pending | pending | pending | not scored in this run | | Maintenance & community | 7% (8.8 this run) | 26 | 85 | Gmail API +59 | | Transparency & trust | 7% (8.8 this run) | 74 | 82 | Gmail API +8 | | Negative events | ≤15 | 0 | 0 | | | **Total** | | **54.1 · C** | **77.8 · BB** | | ## Facts side by side | Fact | Fastmail API (JMAP) | Gmail API | | --- | --- | --- | | Kind | HTTP API | HTTP API | | Vendor | Fastmail Pty Ltd | Google | | Hosted endpoint | no (local only) | `https://gmail.googleapis.com/gmail/v1` | | Transports | HTTP | HTTP, Streamable HTTP | | Auth | OAuth or key | OAuth | | Pricing | Paid | Free | | x402 | no | no | | Licence | Proprietary service under Fastmail's API Terms of Service and API Developer Policy. JMAP is an open IETF standard, and the sample code on GitHub is MIT | Apache-2.0 (client libraries) | | Tools exposed | none | 23 | | Read-only variant documented | yes | no | | llms.txt | no | no | | Last release | 2026-04-22 | 2026-09-23 | | Terms last updated | no date given | 2021-11-09 | | Privacy policy last updated | no date given | 2026-10-01 | | Customer content may train models | not found in the text | yes | | Terms restrict automated access | not found in the text | yes | | Terms restrict benchmarking | yes | not found in the text | | Terms or service can change without notice | not found in the text | not found in the text | | Arbitration or class-action waiver | not found in the text | not found in the text | | Popularity | 123 stars | 12k stars, 1.1M npm/wk | ## Verdicts **Fastmail API (JMAP).** A mailbox API built on the open JMAP standard, with read-only tokens, six OAuth scopes and an MCP server that separates read, write and send access. Fastmail publishes no OpenAPI file, SDK, API changelog, request rate limit or SLA, and its customer terms forbid programmatically generated email to addresses outside the account. **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. ## Before you call either ### Fastmail API (JMAP) 1. Fetch `https://api.fastmail.com/jmap/session` with `Authorization: Bearer ` first. It returns the API URL, account IDs and the request limits to stay under 2. Ask the owner for a read-only token unless the task writes. Sending needs both the Email and Email submission scopes 3. Request only the `properties` you need. Body text is not returned unless `fetchTextBodyValues` is set, and `maxBodyValueBytes` caps it 4. Sync with `Email/changes` from a stored state. On `cannotCalculateChanges`, fetch again from scratch 5. Do not send generated mail to outside recipients without the owner's review. The customer terms forbid it, and trial accounts stop at 120 messages a day ### Gmail API 1. Ask for the narrowest scope. `gmail.labels` is non-sensitive and `gmail.send` is sensitive, while every scope that reads mail is restricted 2. List with `messages.list` and `q` in Gmail search syntax, then fetch each ID with `format=metadata` or `full`. List calls return IDs only 3. Send by posting an RFC 2822 message, base64url encoded, in `raw`. Set `threadId` and matching reply headers to stay in a thread 4. Store the `historyId` and call `history.list`. On a 404, run a full sync. Call `watch` again at least every 7 days 5. Back off exponentially on 403 and 429 rate errors, and keep batches to 50 requests or fewer ## Questions ### Which is better for AI agents, Fastmail API (JMAP) or Gmail API? Gmail API scores 77.8 (BB) on agent readiness against Fastmail API (JMAP)'s 54.1 (C), and leads in every scored category. ### Do Fastmail API (JMAP) and Gmail API need an API key? Fastmail API (JMAP) takes an API key or an OAuth sign-in. Gmail API uses an OAuth sign-in. ### Can an agent call Fastmail API (JMAP) and Gmail API without installing anything? No hosted endpoint is listed for Fastmail API (JMAP). Gmail API has a hosted endpoint at https://gmail.googleapis.com/gmail/v1. ## For agents - This comparison as JSON: https://www.anchorterminal.com/compare/fastmail-vs-gmail-api.json, and with the fewest tokens: https://www.anchorterminal.com/compare/fastmail-vs-gmail-api.min.md - Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "fastmail", "b": "gmail-api"}`. From a terminal: `anchor compare fastmail gmail-api` - Each listing in full: https://www.anchorterminal.com/api/v1/tools/fastmail.json and https://www.anchorterminal.com/api/v1/tools/gmail-api.json ## Other comparisons with Fastmail API (JMAP) or Gmail API - [EmailEngine vs Fastmail API (JMAP)](https://www.anchorterminal.com/compare/emailengine-vs-fastmail.md) - [EmailEngine vs Gmail API](https://www.anchorterminal.com/compare/emailengine-vs-gmail-api.md) - [Fastmail API (JMAP) vs Nylas Email API](https://www.anchorterminal.com/compare/fastmail-vs-nylas-email.md) - [Fastmail API (JMAP) vs Outlook Mail (Microsoft Graph)](https://www.anchorterminal.com/compare/fastmail-vs-outlook-mail-graph.md) - [Fastmail API (JMAP) vs Unipile](https://www.anchorterminal.com/compare/fastmail-vs-unipile.md) - [Fastmail API (JMAP) vs Zoho Mail API](https://www.anchorterminal.com/compare/fastmail-vs-zoho-mail.md) - [Gmail API vs Nylas Email API](https://www.anchorterminal.com/compare/gmail-api-vs-nylas-email.md) - [Gmail API vs Outlook Mail (Microsoft Graph)](https://www.anchorterminal.com/compare/gmail-api-vs-outlook-mail-graph.md) - [Gmail API vs Unipile](https://www.anchorterminal.com/compare/gmail-api-vs-unipile.md) - [Gmail API vs Zoho Mail API](https://www.anchorterminal.com/compare/gmail-api-vs-zoho-mail.md)