The API launch checklist (with templates)

The single biggest reason API launches go poorly isn't the API itself. It's the launch surface — docs, SDKs, examples, support paths, status, changelog — being half-built when developers land on it. This is the checklist that holds up across a few dozen API launches we've seen in 2026.

Treat it as a gate, not a wishlist. Each item maps to a real customer failure mode if it's missing.

Spec hygiene (the foundation)

• OpenAPI 3.0 or 3.1 spec exists, lives in the API repo, single source of truth.
• Every operation has an operationId in consistent casing.
• Every schema lives in components/schemas, referenced not inlined.
• Every operation has at least one request example and one response example.
• Security schemes are defined and applied; no operation marked as auth-required has a missing security block.
• Spec validates: swagger-cli validate, spectral lint, or redocly lint passes with no ERR-level findings. (oasdiff is a diff tool, not a single-spec validator — use it for breaking-change detection between versions, not initial validity.)

If any of these are missing, the rest of the checklist gets harder. Fix the spec first. See OpenAPI best practices for SDK-friendly specs.

SDKs

• TypeScript SDK published to npm, semver versioned.
• Python SDK published to PyPI, semver versioned.
• Both SDKs ship type hints visible to mypy/pyright (Python) and TypeScript (TS).
• Errors are typed: APIError with status, code, message, ideally body.
• Pagination has helpers; customers don't have to manually handle cursors.
• First-party README for each SDK with install + quickstart + error model.

Hand-written SDKs are fine pre-launch; generated SDKs scale better. Generate a TypeScript SDK from OpenAPI and Generate a Python SDK from OpenAPI cover the generation paths.

Docs

• API reference page exists per endpoint group, generated from OpenAPI.
• Quickstart: ten lines, from signup to first successful call.
• Authentication doc covers every supported method (bearer, OAuth, API key).
• Errors doc lists every error code with one-line meaning and remediation.
• Versioning policy doc explains how breaking changes are communicated and the support window for deprecated versions.
• Pricing doc is public and matches what the dashboard charges (sounds obvious; we've seen it not match).

Examples

• At least one runnable example per endpoint.
• Examples kept in a directory in the API repo, run in CI on every deploy.
• Examples embedded into docs via include directives, not copy-paste duplicates.

The cheapest way to break trust: ship a docs example that doesn't work. The cheapest way to keep trust: run them in CI.

Operational

• Status page exists. Real uptime, not vaporware.
• Incident response process: who gets paged, what's the SLA, where do customers see updates.
• Rate limits are documented and enforced. 429 responses include Retry-After headers.
• Idempotency keys supported for at least every mutating endpoint with an obvious retry pattern (POST creating resources).
• CORS policy explicitly set (allow-list, not wide open).
• HTTPS enforced; HSTS header set; no plain-HTTP fallback.

Agent-readable

• /llms.txt at the root of the docs site, generated from OpenAPI, regenerated on every spec push.
• Per-page Markdown alongside HTML for every reference page.
• robots.txt allows AI-agent user-agents you actually want crawling you (OpenAI, Anthropic, Google).
• sitemap.xml lists every public docs page.

If you've never thought about llms.txt: What is llms.txt? is the starting point. Coding agents are the first reader of your API in 2026.

Changelog

• Changelog page exists at /changelog/ (or somewhere obvious).
• Every API change has a date, a category (breaking / non-breaking / fix), and one-line description.
• Breaking changes have a migration note linking to the old behavior.
• SDK releases are tagged with the spec version that produced them.

Support

• Public contact path: email, form, or Slack/Discord community.
• Internal ticket triage: who owns the first response, what's the target turnaround.
• Pre-canned answers for the top five anticipated questions.
• Documented escalation path for production incidents.

Day-one monitoring

What to watch in the first 24 hours:

• Signup → first-API-call conversion rate. If it's well under what your peers report (developer-tool norms are around 30–50%), your quickstart is broken.
• 4xx rate per endpoint, segmented by error code. Spikes on 401 mean docs auth section is unclear; spikes on 422 mean schema validation isn't aligned with examples.
• 5xx rate. Anything above background noise is a bug.
• SDK download counts on npm and PyPI. Low downloads with high API calls means customers are calling the API directly because the SDK is broken or unclear.
• Time-to-first-error per customer. Long means good onboarding; short and clustered around the same endpoint means a docs gap.

The two things you can skip on day one

Plenty of API launch checklists tell you to ship interactive playgrounds, in-portal API logs, SOC 2 reports, and a partner program before going live. You can't ship all of that pre-revenue.

• Interactive playground. Curl from a quickstart works. Ship a playground at the 100-customer mark.
• In-portal API logs. Customer-facing logging is a year-two feature. Server-side observability for support is on the checklist (above); customer-self-serve isn't.

What this looks like in practice

If you're using OpenAPI + a hosted docs/SDK pipeline (Bloom, Fern, Stainless), this checklist collapses to:

1. Get the spec clean.
2. Run the pipeline.
3. Review the docs preview before publishing.
4. Set up status + changelog manually.
5. Hit go.

If you're rolling your own: this checklist is one or two engineer-quarters of work. Plan accordingly.

Try Bloom free for 30 days — generates docs, SDKs, llms.txt, and per-page markdown from your OpenAPI spec; previews everything before publishing. Completely free for 30 days. No credit card required.