Do I need a tool for API documentation or can I write it manually?

You can absolutely write API documentation manually — you do not need a tool.
But whether you should depends on the size of your API and how often it changes.

Write it manually if:

• Your API is small or simple
• You have only a few endpoints
• Changes are infrequent
• You want full control over wording and structure

Use a tool if:

• Your API has many endpoints
• You want docs generated from code or an API spec
• Your API changes often
• You want interactive docs, examples, or auto-updated references

Common approaches

• Manual docs: Markdown, Notion, Confluence, Google Docs, README files
• Spec-first tools: OpenAPI/Swagger, API Blueprint
• Doc generators: Swagger UI, Redoc, Stoplight, Postman
• Code-based tools: JSDoc, Sphinx, Docusaurus with generated content

Practical recommendation

A good middle ground is:

1. Define your API in OpenAPI
2. Use a tool to generate the reference docs
3. Add manually written guides, tutorials, and examples around it

That gives you accuracy and maintainability without losing the human-friendly parts.

If you want, I can help you choose between manual docs vs OpenAPI vs a documentation tool based on your API size and workflow.