Nylas Calendar and Scheduler API by Nylas

# Fix list: Nylas Calendar and Scheduler API

From Anchor Terminal's listing at https://www.anchorterminal.com/tools/nylas-calendar, the October 2026 research run, assessed 1 October 2026. Grade BB, 71.3 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 Calendar and Scheduler 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, such as $1.50 a calendar-only account a month on Pro (20). Free plan with 5 connected accounts and no card (20). Keys can be minted by API, but only through a Service Account a person sets up after a browser signup (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. Security & auth, 59 out of 100, up to 7.2 more on the total

Why it scored 59: Application API keys can be created with an expiry, rotated and revoked through the admin API, but a key can't be scoped, and it reaches every grant in the application. End users connect through OAuth with scopes the app picks (22). No read-only key or per-grant MCP mode. The MCP takes the whole application key, though sends need a confirmation step (8). The MCP docs warn that email, documents and calendar events can carry hidden instructions to send mail or leak credentials (13). No operator request log found in the docs we read (0). SOC 2 Type II, ISO 27001 and 27701, CSA STAR, an annual penetration test and a private bug bounty with security@nylas.com, but no security.txt, per the 30 September check (16).

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.

## 3. Reliability, 75 out of 100, up to 5 more on the total

Why it scored 75: Atlassian Statuspage at status-v3.nylas.com with US and EU components (20). The RSS history shows several incidents since 3 July, all on email, IMAP, webhooks or Notetaker rather than calendar, among them about six hours of IMAP retrieval and webhook degradation on 10 September, five hours of missing EU message webhooks on 24 July and elevated Microsoft send and read errors on 1 September. We scored between the minor and major bands because none touched calendar (15). 200 requests a second per grant for calendar and 50 a second per application for grant, auth and webhook endpoints, plus the provider limits behind them (15). 429s pass on the provider's Retry-After when there is one, and the errors page says which codes to retry with exponential backoff. Idempotency keys cover email send only, not event writes (10). Enterprise lists a guaranteed uptime SLA with no published figure (5). 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.

## 4. Agent ergonomics, 71 out of 100, up to 4.7 more on the total

Why it scored 71: 38 MCP tools with no toolsets found (5), plus 5 for `limit` and `select` field selection on the REST API (10). Page tokens and time filters on event lists (18). Typed errors with a request ID and a provider error passed through, and a retry table (18). The MCP needs a confirmation call before sending mail and says deletes need user consent, but event writes have no idempotency key and we found no tool annotations (10). Official SDKs in Node, Python and more (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.

## 5. Transparency & trust, 79 out of 100, up to 1.8 more on the total

Made of editorial 67, provenance 90.

Why it scored 79: Closed service under Californian law, with MIT SDKs (15). The privacy policy keeps customer data for the life of the account plus two months and lets EEA customers pick UK or US data centres, per the 30 September check. A sub-processor page was updated on 28 August 2026 with a status notice (24). v2 deprecation documented and a dated changelog, but no deprecation policy found (10). Sub-processors listed, AWS and GCP named as hosts, US and EU regions (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):

- security.txt: not found (0 of 10)

## 6. Schema & documentation, 91 out of 100, up to 1.5 more on the total

Why it scored 91: OpenAPI spec, per the 30 September check (25). llms.txt and Markdown docs (10). Guides say when to use each API, but we couldn't read the MCP tool descriptions (15). Typed parameters in the reference (12). An errors page with a JSON shape (`type`, `message`, `provider_error`, `request_id`) and a retry yes or no for each status code (14). v3 in the path and a dated changelog with 20 entries between 20 August and 28 September 2026 (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: nylas-python v6.18.0 on 30 September 2026 and changelog entries up to 28 September (30). At least 20 dated changelog entries and Python releases on 21 July and 30 September since 3 July (20). Public dated changelog, open SDK repositories with commits through August and September, and support (15). Current official SDKs (15). The Node SDK's last npm release is v8.4.0 from 24 June 2026, with later fixes, including one that stops sending the API key as `client_secret` in the OAuth token exchange, not yet published (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.

- Whether the dashboard keeps a per-request log an operator can read
- unchecked: the OpenAPI spec contents this run
- Whether the MCP tools carry readOnlyHint or destructiveHint
- Enterprise SLA figure
- When the Node SDK fixes merged after v8.4.0 will be published

## Weaknesses

- API keys can't be scoped, so the MCP and any agent holding a key reach every grant
- No idempotency key on event writes, only on email send
- Several status incidents since July on email, IMAP and webhooks, including about six hours on 10 September
- Extra connected accounts cost $1.50 to $2.25 a month each
- No security.txt on nylas.com

## 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 calendar calls to /v3/grants/<grant_id>, one grant per connected account
- List events in the window before retrying a create, since event writes have no idempotency key
- Point the MCP client at mcp.eu.nylas.com if the application lives in the EU region
- On 429, use the passed-through `Retry-After` if present, otherwise back off per grant
- Mint a short-lived API key for the agent with `expires_in` rather than sharing the main one

## What the review panel asked for

- Idempotency key on events
- Calendar-only toolset
- per-grant keys
- calendar-only toolset

## 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.