Move your API docs to the wrong kind of tool and you'll rebuild the same pages twice, once for people and again for the AI agents that now read them. Hosted platforms, open-source static generators and OpenAPI-first reference tools each replace a different part of a developer hub, so match the tool to the part your readers rely on most.
ReadMe sells itself as developer-friendly API documentation, with guides, an API reference, a changelog, an AI agent linter and an MCP server in one hosted product. If you're leaving it, you're probably giving up that all-in-one setup on purpose, which makes a quick hands-on comparison worth far more than reading feature pages. So this page starts with the trial, then sorts the eight tools by how they're built.
One afternoon, two docs tools, the same endpoint
- Export one real endpoint, one how-to guide and the OpenAPI file behind them from your current docs.
- Choose two tools from different build types further down this page, such as one hosted platform and one spec-first reference tool.
- Load the same spec and the same guide into both, and note every page you had to fix by hand.
- Ask an AI assistant to answer a question about that endpoint from each published version, and compare what it gets right.
- Change one parameter in the spec, publish again, and check how each tool shows that change to a returning reader.
That's a few hours of work, and it tells you three things no feature list will. You see how much of your current content moves without rewriting. You see how each tool treats a reader who's an AI agent rather than a developer. And you see what happens on the day the API changes, which is when stale docs start hurting the people who depend on them.
Keep your notes short and specific. A line such as the auth example rendered wrongly and took twenty minutes to fix is worth more than a general feeling that one tool looked nicer. If both tools pass, the tie-breaker is usually the second step of your own workflow: who writes the guides, where the spec lives, and who presses publish.
One more thing to record while you're there: how the guide reads next to the reference. Many teams move docs because their written guides and their generated reference drift apart over time, so it's worth noticing whether each tool keeps them in one place or treats them as two separate sites.
Three ways these docs tools are built
The eight split cleanly by build type, and that matters more than any single feature. The hosted platforms run your docs for you. You write, they publish, and the hosting, search and updates are their job. That's the closest match to what you're leaving, and the easiest move for a small team without someone to look after a build. The trade-off is that your docs live on someone else's platform, so check how easily you could export them again if you ever moved on.
The open-source static generators are a different deal. They turn files in your repository into a docs site you host yourself. You get full control over where the site lives and how it looks, and you take on the build, the hosting and the search set-up that a hosted platform would handle for you. In this list that means MkDocs, which builds from Markdown and one config file, and Starlight, which sits on the Astro framework. Both suit teams who already treat docs as code and review changes in pull requests.
The OpenAPI-first reference tools start from your API description and grow everything else from it. Redocly and Bump.sh build reference docs and portals around the spec, with extras such as a changelog or linting, and a third tool in this group generates SDKs and MCP servers from the same file. If your spec is the most reliable thing your team maintains, this group is where to look first.
Docs written for machine readers too
The bigger change in this category has nothing to do with themes or editors. Docs are now read by AI agents as well as people, and the vendors know it. The platform you're leaving, Mintlify, GitBook, Scalar and Fern each now lead their own pages with AI agents, llms.txt files or MCP servers. So the useful comparison isn't which one looks best in a browser. It's how well each one serves a machine that's trying to call your API correctly.
That's why step four of the trial above matters. Point an assistant at each published version and ask it something specific, such as which header an endpoint needs. If the answer comes back wrong from one tool and right from the other, you've learned more than a week of reading would teach you. Then check what each tool publishes for agents, whether that's an llms.txt file or an MCP server, and whether it updates when your spec does.
Eight docs tools by name
Listed in no particular order beyond the alphabet, with each maker's own claims marked as theirs. Each line is a short description, not a review.
Bump.sh
Best for: Turning OpenAPI and AsyncAPI documents into doc portals, with an automated changelog, versioning and governance alongside.
Fern
Best for: Producing documentation sites, SDKs and a CLI from your API definition, with search, an MCP server, llms.txt and AI search built in, per the vendor.
GitBook
Best for: Hosted docs that flag outdated pages and suggest fixes; vendor claim: it flags outdated content, then fixes it.
Mintlify
Best for: Startups and enterprises after a hosted platform whose docs, the vendor says, stay current for AI agents as well as human readers.
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MkDocs
Best for: Project documentation written in Markdown and built as a static site from one YAML config file, with built-in and third-party themes.
Redocly
Best for: API reference work built on an open-source CLI and the Redoc reference-docs project, for teams who want their docs tooling partly in the open.
Scalar
Best for: Teams whose OpenAPI file is the source of truth and who want hosted MCP servers that stay in step with it as the spec changes.
Starlight
Best for: Docs sites built on the Astro framework with navigation, search and translation support, writing in Markdown, Markdoc or MDX.
Build type and reader at a glance
| Tool | Build type | Good match for |
|---|---|---|
| Bump.sh | API doc portal | Teams publishing changelogs from their specs |
| Fern | Docs plus SDK generator | Generating docs and SDKs from one definition |
| GitBook | Hosted docs and knowledge base | Keeping a knowledge base from going stale |
| Mintlify | Hosted docs platform | Startups wanting hosted, self-updating docs |
| MkDocs | Open-source static generator | Markdown project docs with one config file |
| Redocly | API docs platform | Reference docs grown from an open-source project |
| Scalar | API reference and SDKs | MCP servers kept in step with a spec |
| Starlight | Open-source docs framework | Astro sites needing docs with search |
Moving a developer hub without losing readers
Keep the old hub live until the new docs have been published, checked by an outside developer and read by an AI assistant without errors. Then redirect page by page rather than all at once. If you want a broader look at the category, my roundup of API documentation tools covers more options, and if a knowledge base matters as much as reference pages to you, there's a separate guide to knowledge base and docs platforms.
Whichever group you pick, give one person the job of owning the docs after the move. Tools don't stop docs going stale on their own; someone still has to notice.
Do you make documentation tools for developers? Tool makers can ask to be considered for a featured place on this list.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
Can I move my existing guides as well as the API reference?
Usually, but guides tend to need more hand-fixing than reference pages, which are generated from the spec. Move one real guide during the trial and see how much rewriting it needs.
Should I host my own docs or use a hosted platform?
Host your own if your team already reviews docs in pull requests and can look after a build. Use a hosted platform if you'd rather nobody had to think about hosting, search or updates.
What is llms.txt and do I need one?
It's a plain-text file several docs tools publish to help AI models read a site. If AI agents use your API, it's worth checking which tools create one for you.
Do these tools work from an OpenAPI file?
The spec-first reference tools are built around one, so ask whether each hosted platform imports one too. Load your own file during the trial rather than relying on a general claim.
How do I avoid broken links when I move?
Keep a list of every public docs URL before you start, then redirect each one to its new home as it goes live. Moving everything on one day is how readers end up on error pages.
