Adding a third-party API can save weeks of work. It also creates a dependency that can break your product, inflate your bill or block a feature launch. This checklist is what we use when adding APIs to the apimark directory.
Fit
- Does it do exactly the job? Run your three hardest real inputs through it before reading the marketing page. Edge cases reveal more than demos.
- Is the data fresh and accurate enough? Ask how often it updates, where it comes from, and whether the source is authoritative.
- Latency and regions. Measure p95 response time from where your servers run, not from your laptop.
Cost
- Model the bill at 10× your current volume. Per-request pricing that's trivial today can dominate costs later. Look for overage rates, minimum commitments and charges for failed calls.
- Understand the free tier. Is it for development only? Is commercial use allowed? Are there hard caps or surprise charges?
- Rate limits. Requests per second, per day and per month, plus how limits are reported (headers such as
Retry-After) and whether bursts are allowed.
Reliability and trust
- Status page and incident history. A public status page with honest post-mortems is a good sign.
- Versioning and deprecation policy. How much notice will you get before breaking changes? Is there a changelog?
- Documentation quality. Runnable examples, an OpenAPI spec, SDKs in your language and clear error codes all reduce integration time.
Legal and data
- Terms of use. Can you cache, store or display the data? Are attribution or branding rules required (common with maps, weather and photo APIs)?
- Privacy and security. If you send personal data, check data-processing terms, where data is stored, retention, and compliance claims relevant to you (GDPR, SOC 2 and so on).
Exit
- Plan your exit on day one. Wrap the API behind your own interface, store results you're allowed to keep, and identify at least one alternative. The directory groups APIs by category to make that easy.
A quick scoring template
| Criterion | Weight | Score 1–5 |
|---|---|---|
| Fit and accuracy | ×3 | |
| Cost at 10× scale | ×2 | |
| Reliability and versioning | ×2 | |
| Docs and developer experience | ×1 | |
| Terms, privacy, exit | ×2 |
Anything scoring under 30 out of 50 deserves a second look at alternatives, or at building that piece yourself.