Do I need a docs site if my API is only for internal use?

Usually, yes — but it can be much lighter than a public docs site.

Even for an internal API, some kind of documentation is valuable because it helps with:

• Discoverability: people can find what exists without asking around
• Consistency: teams use the API the same way
• Onboarding: new engineers ramp up faster
• Fewer interrupts: less “how do I use this endpoint?” Slack traffic
• Change management: easier to see deprecations, versions, and breaking changes

That said, you may not need a full-blown polished docs site if:

• the API is tiny and used by one team
• usage is stable and rarely changes
• there’s a single owner who can answer questions quickly
• the consumers are all close to the codebase

A good internal middle ground

Instead of a public-style docs portal, consider:

• an OpenAPI/Swagger spec
• a README with setup/auth/examples
• generated interactive docs for testing
• code samples and common workflows
• a short section on errors, rate limits, and auth
• a changelog for breaking changes

Rule of thumb

If more than one person or one service depends on the API, some docs are worth it.
If it’s truly a small, single-team, low-change internal utility, a solid README and spec may be enough.

If you want, I can help you decide what level of documentation makes sense for your specific API size and team setup.