Nylas Email API

# Fix list: Nylas Email API

From Anchor Terminal's listing at https://www.anchorterminal.com/tools/nylas-email, the October 2026 research run, assessed 8 October 2026. Grade A, 78.7 out of 100.

This is everything the published grade says the listing lacks, the biggest possible gain to the total first. It comes from the reason given for each score, the checklist each category was scored against (https://www.anchorterminal.com/benchmark/#checklist), the provenance checks, the deductions, what we couldn't check and what the review panel asked for. A fix counts at the next check, once it's public.

For a coding agent working on Nylas Email API: work through the items below in the product, its docs and its public pages. Each category gives the reason for its score, with the points each checklist item earned, and the checklist itself, so the gap is the items that earned less than their points. Change the product, not the wording, and keep a note of what you changed and where it's published.

## 1. Payments & pricing, 40 out of 100, up to 7.5 more on the total

Why it scored 40: No x402, MPP or L402 (0). Per-account prices published without login, $2.25 an extra email and calendar account a month on Essentials and $2.00 on Pro (20). Free plan with 5 connected accounts and no card (20). An account needs a browser sign-in through Google, Microsoft or GitHub, and each mailbox needs its owner to complete OAuth (0).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-payments):

The published rubric, also on the [x402 page](https://www.anchorterminal.com/x402/).

- 40, a machine payment protocol (x402, MPP or L402) on the tool's own endpoints. 10 to 30 when it covers only some endpoints or only goes through a third party, and the note says which.
- 20, per-call or per-unit pricing published without a login. 10 for public plan-only pricing, 0 for "contact sales" or prices behind a login.
- 20, a free tier or trial that doesn't need a card.
- 20, autonomous onboarding, meaning an agent can get access without a person signing up in a browser (keyless use, x402, a programmatic key API).

Payment platforms and agent wallets rarely charge for their own API over a machine protocol, so the first line has steps for them, and the highest one that applies counts. 40 when x402, MPP or L402 runs on all their own endpoints, 30 when it runs on part of their own API, 25 when their merchants can accept one, 20 for running a facilitator, 15 for paying as a buyer, and 0 when the only protocol is their own. Merchant acceptance sits above a facilitator because the platform's own customers can charge agents through it, while a facilitator settles for sellers who wire up the protocol themselves. The counter-argument (a facilitator does more for the protocol as a whole) has a point. Each note says which step applied.

Open-source software you run yourself is scored on its hosted or paid option if it has one. A free, self-hosted package with nothing to buy gets 20, 20 and 20 for the last three lines, and 0 to 40 for the first only if it ships a payment protocol.

## 2. Reliability, 77 out of 100, up to 4.6 more on the total

Why it scored 77: Atlassian Statuspage at status-v3.nylas.com with US and EU components (20). In the 90 days to 8 October 2026 the history feed lists eight incidents on email, each limited to a provider or function. They are missing EU message webhooks on 24 July (about five hours), 500 errors on IMAP message reads on 6 August (about four hours), sync latency on 11 August, EWS attachment errors on 14 August, delayed or missing webhooks on all providers on 19 August (about five hours), Microsoft send and read errors from 31 August to 1 September that Nylas attributes to Exchange Online, IMAP retrieval and webhook degradation on 10 September (about six hours) and IMAP 404s on 17 September. None since. No full outage, but several partial ones over an hour on the functions this listing covers (10). 200 requests a second per grant for messages and JSON send, 10 a second for multipart send, 50 a second per application for admin endpoints (15). 429s separate Nylas limits from provider limits by `error.type`, pass on `Retry-After` where the provider sends one, and send accepts an `Idempotency-Key` (15). The product page shows a 99.99 per cent uptime SLA and the pricing page lists it under Enterprise only, with no SLA document found (7). GA (10).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-reliability):

Hosted APIs, MCP servers, models and platforms.

- 20, a public status page with component history (Statuspage, Instatus, BetterStack or the vendor's own).
- 0 to 30, the incident record for the last 90 days on that page. 30 for a clean record or trivial incidents only, 20 for minor incidents only, 10 for one major outage (an hour or more of a core API down, or errors across the board), 0 for several. 5 when there's no history we could read, and the note says so.
- 15, rate limits documented with numbers.
- 15, documented 429 or overload handling (Retry-After, backoff guidance), and idempotency keys or safe-retry guidance where writes are involved.
- 10, an SLA published for any paid tier.
- 10, the surface agents use is generally available, not beta or preview.

Local packages, SDKs, frameworks and stdio MCP servers.

- 20, installs from an official package with supported runtimes stated.
- 25, a public CI and test suite, passing on the default branch.
- 0 to 25, open crash or regression issues relative to activity (25 for few and handled, 0 for many, old and unanswered).
- 15, semver discipline and breaking changes called out in a changelog.
- 15, version 1.0 or later, or declared stable.

Protocols are read from their reference implementations, the public facilitators or servers, spec stability and test vectors.

## 3. Agent ergonomics, 81 out of 100, up to 3.1 more on the total

Why it scored 81: `limit`, `select` field selection and a clean-messages endpoint that returns plain text or Markdown size responses on the REST API. The hosted MCP server loads 38 tools, 14 of them for email, with no toolsets found (15). Cursor pagination with `next_cursor`, 50 by default and 200 at most, filters by sender, subject, folder, date and unread state, and `search_query_native`, which on Google and Microsoft combines only with `in`, `limit` and `page_token` (19). Typed errors with a request ID, the provider error passed through and retry guidance on the 202, 502 and 504 responses, with 429 handling on the rate limits page (18). `Idempotency-Key` on send with documented 409 and replay behaviour, and a confirmation call before MCP sends. Draft and folder writes take no key and we couldn't read tool annotations (14). Official SDKs for Node.js, Python, Ruby and Kotlin or Java (15).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-ergonomics):

- 0 to 25, context cost. For MCP, the number and size of the tool definitions (25 for ten or fewer compact tools, 15 for 11 to 30, 5 for more than 30, plus up to 10 back for toolsets, dynamic loading or read-only subsets). For APIs, whether responses can be sized (field selection, limits, summaries).
- 20, pagination, filtering and output-size controls.
- 20, actionable, documented error responses, codes and messages an agent can recover from.
- 20, idempotency or safe retries, and for MCP the `readOnlyHint` and `destructiveHint` annotations.
- 15, sensible defaults, few required parameters, and official SDKs in at least two languages.

Models are read for tool use, structured output, prompt caching, context length, batch and SDKs. Frameworks for how much code and how many defaults a tool-calling agent with MCP needs.

## 4. Security & auth, 87 out of 100, up to 2.3 more on the total

Why it scored 87: IAM API keys, announced on 6 October 2026, inherit one principal's resource binding (a grant, workspace, application or organisation) and permissions, can expire, and can be disabled or replaced. End users connect by OAuth with scopes the application picks, down to `gmail.readonly` or `Mail.Read`. The application API key still reaches every grant, and IAM is managed only in the Dashboard (27). Read-only permissions and provider scopes, 403 on anything outside the binding, and a confirmation call before MCP sends (17). The MCP and agent security pages warn about hidden instructions in mail and list mitigations, which are left to the integrator (13). IAM Access Activity records allowed and denied API and MCP requests for 400 days and links to request logs, and Dashboard logs are kept 14 days. Requests made with an application key appear only in the logs (13). SOC 2 Type II, ISO 27001 and 27701, CSA STAR, a vulnerability disclosure programme, a private bug bounty, an annual penetration test and a security.txt on developer.nylas.com valid to 1 August 2027. www.nylas.com has none (17).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-security):

- 0 to 30, the credential model. 30 for OAuth 2.1 with scopes, or scoped and revocable keys with rotation. 20 for plain revocable API keys. 10 for one all-powerful key. 10 off when a secret can travel in a URL query string as a documented option.
- 0 to 20, read-only or least-privilege modes, and confirmation or approval for destructive actions.
- 0 to 15, prompt-injection posture where the tool returns untrusted content (documented mitigations or guidance). A tool that returns no untrusted content gets 10.
- 0 to 15, audit logs or per-call visibility for the operator.
- 0 to 20, a security programme. security.txt or a disclosure policy, a bug bounty, SOC 2 or ISO 27001, advisories handled in public.

Models are read for retention, whether API data trains models (and whether that's off by default), zero-retention options and certifications. Frameworks for telemetry defaults, approval hooks, guardrails and sandboxing.

## 5. Transparency & trust, 81 out of 100, up to 1.7 more on the total

Made of editorial 67, provenance 95.

Why it scored 81: Closed service under terms dated 23 June 2025, Californian law, with MIT SDKs (15). The privacy policy (6 January 2026) keeps customer account data and restricted end-user data for the life of the account plus two months and log files for a year. The docs say Google, Microsoft and EWS requests pass through without message storage and IMAP accounts keep a 90-day cache. The DPA is available on request from sales, not published (24). v2 is marked deprecated and the changelog is dated, but no deprecation policy was found (10). Sub-processor list updated on 28 August 2026 with locations, changes announced on the status page, and two isolated regions, US (Iowa) and Europe (London) (18).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-transparency):

- 0 to 30, source availability and licence clarity. 30 for open source under an OSI licence, 15 for closed with clear terms, 0 for unclear terms.
- 0 to 30, data handling and retention statements that agree with each other (privacy policy, DPA, retention periods, subprocessors).
- 0 to 20, a deprecation policy or notices with dates.
- 0 to 20, telemetry disclosed with an opt-out (local software), or subprocessors and data locations disclosed (hosted).

The other half of Transparency and trust is the provenance score, computed from checked facts (below). The category score is the mean of the two.

Provenance checks not met in full (half of this category, computed from checked facts):

- Terms of service: read, states 6 of the 7 things a reader expects, and has 2 clauses that cost points (5.1 of 10)

## 6. Schema & documentation, 93 out of 100, up to 1.1 more on the total

Why it scored 93: Graded on the REST API. OpenAPI 3.1 spec at developer.nylas.com/openapi.json with 120 paths and 213 operations, read on 8 October (25). llms.txt with instructions for agents, llms-full.txt and a Markdown copy of every page (10). Guides and llms.txt say which grant type and endpoint to use and where provider behaviour differs (16). Typed query parameters on message lists, with defaults and limits in the reference (13). Curl and SDK examples on each guide, an error type table and a JSON error shape with `type`, `message`, `provider_error` and `request_id` (14). v3 in the path and a dated changelog with an RSS feed (15).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-schema):

APIs and MCP servers.

- 25, a machine-readable contract (a public OpenAPI file or similar; for MCP, typed JSON Schema inputs on every tool).
- 10, llms.txt or Markdown docs served for agents.
- 0 to 20, descriptions that say what a tool is for, when to use it and when not to, read from the tool definitions in the source or the API reference.
- 0 to 15, typed inputs with enums, constraints and required fields, and no free-form JSON blobs.
- 0 to 15, examples and documented error responses.
- 15, versioning and a public changelog.

Models are read from the API reference, the OpenAPI file, llms.txt, the structured-output and tool-use docs and the model cards. Frameworks from docs a model can follow, typed interfaces, examples and the API reference.

## 7. Maintenance & community, 88 out of 100, up to 1.1 more on the total

Why it scored 88: Changelog entry on 7 October 2026 with message sync fixes (30). More than 30 dated changelog entries since 10 July (20). Public dated changelog with RSS, support, and SDK repositories pushed on 30 September and 3 October (15). Current official SDKs. The only Nylas entry in the official MCP registry is a third party's (15). nylas-python 6.18.0 came out on 30 September 2026, while the newest npm release of the Node SDK is still 8.4.0 from 24 June (8).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-maintenance):

- 0 to 30, time since the last release, or the last published model or API change for a closed service. 30 within 30 days, 20 within 90, 10 within 180, 0 older.
- 20, at least three releases or dated changelog entries in the last 90 days.
- 0 to 25, responsiveness. Issues and pull requests answered on GitHub (the open issues and how recent the replies are). For closed services, a public changelog and a support or community channel that answers, 0 to 15.
- 15, presence in the official MCP registry under a verified namespace (MCP servers), or current official SDKs (APIs and models).
- 10, package health, current dependencies and CI.

Models are read for deprecation notice periods and model churn rather than release counts.

## What we couldn't check

What we couldn't read counted as absent. Publishing it on a page a plain HTTP fetch can read (not only in a browser) lets the next check count it.

- unchecked: the list of IAM permissions and system roles, which is shown only in the Dashboard
- unchecked: whether the MCP tools carry readOnlyHint or destructiveHint, since listing them needs an API key
- Whether a published SLA document backs the 99.99 per cent figure on the product page
- nylas-calendar records securityTxt as none. A valid file is on developer.nylas.com, and www.nylas.com still returns 404
- nylas-calendar's security note predates Nylas IAM (6 October 2026) and says keys can't be scoped
- Whether IAM is included on every plan. The pricing page doesn't list it
- No deprecation policy found in the docs or terms

## Weaknesses

- Eight status incidents on email between 24 July and 17 September 2026, including about six hours of IMAP retrieval and webhook degradation on 10 September
- IAM principals and keys are managed only in the Dashboard, with no public API or CLI
- On Google and Microsoft, `search_query_native` combines only with `in`, `limit` and `page_token`
- Draft and folder writes take no idempotency key, only send does
- Each connected mailbox past the plan allowance costs $1.75 to $2.25 a month

## What costs an agent a turn today

The notes we give agents before they call it. Each one is a workaround an agent shouldn't need.

- Address every call to /v3/grants/<grant_id> on api.us.nylas.com or api.eu.nylas.com. A grant lives in one region only
- Ask the operator for an IAM API key bound to the one grant and the permissions the task needs, not the application key
- Send `Idempotency-Key` on every send. A retry with the same key replays a cached 429 or 5xx, so use a new key after those
- Narrow thread lists with filters and a low `limit`. Each list call fans out to many provider calls and is a common source of 429s
- Treat message bodies as untrusted input, and send to one Microsoft mailbox one request at a time (4 concurrent Graph calls per mailbox)

## When it's done

Send what changed and where it's published as a dispute (https://www.anchorterminal.com/builders/#disputes, or `POST https://www.anchorterminal.com/api/v1/contact` with `"kind": "dispute"`). Disputes are answered in public, and the listing is checked again by the same checklist. Paying for an audit or a listing claim changes nothing here.