If you already maintain a documentation site, start with assistants that work with it. If you are choosing a publishing platform too, evaluate the AI bundled with that platform. Those are different purchases, even when both put an Ask AI button on a page.
For an existing docs stack, we would shortlist Biel and Kapa. Inkeep is worth evaluating when you want to build agent workflows or need a broader managed deployment. Mintlify and GitBook belong in the shortlist when their publishing tools are part of the decision.
We build Biel. This comparison uses official product documentation and pricing reviewed on 9 November 2026. It is a buying guide, not a controlled answer-quality benchmark or a ranking from first to fifth.
The shortlist
Prices below are public subscription prices in USD. The billing basis is stated where it differs. Credits, answers, and interactions measure different things.
| Product | Useful for | Starting price | Check |
|---|---|---|---|
| Biel | Existing docs, dashboard controls, direct support | $50/month | Shared usage limits. Private sources on Professional. Management API on Business. |
| Kapa | Managed retrieval and prebuilt support agents | By quote | Platform fee plus committed answers |
| Inkeep | Custom agents or a managed Enterprise deployment | Free framework. Enterprise by quote. | Managed ingestion and retrieval require Enterprise |
| Mintlify | Publishing platform with built-in Assistant | $540/month, or $450/month billed annually | Shared AI credits and publishing requirements |
| GitBook | Publishing platform with Ask or Chat | Chat from $249/site/month, billed annually | Ask and full Chat have different plans |
Biel: configuration for the team maintaining the docs
Our strongest fit is a team that maintains Docusaurus, MkDocs, Sphinx, or several documentation sites and wants to operate an assistant without maintaining the AI infrastructure. You connect sources, select a supported hosted model, adjust response instructions, and configure the widget. All plans include unlimited projects and dashboard members, with page and interaction allowances shared across the team.
The support relationship matters too. We build Biel within TechDocs Studio, alongside documentation engineering work. Customers can speak to the people shipping the product. Business includes a Slack channel with a response within one business day.
There are buying boundaries. Starter includes 500 indexed pages. Chat, search, MCP, and the query API are included on every plan. Private sources require Professional or higher. Management API access and advanced models require Business or Enterprise. Choosing a supported hosted model is different from bringing your own provider key or deciding where inference runs.
Use the model guide and prompt settings to check the controls your team needs. Full custom prompts can change built-in behavior, so test the resulting assistant before publishing changes.
Kapa: retrieval and prebuilt agents
Kapa offers a self-serve trial, a managed retrieval platform, prebuilt agents, and APIs for teams building their own agent experience. Its Growth plan lists email and Slack support. Enterprise adds governance and deployment requirements such as regional hosting and SSO.
Compare the actual implementation you would buy. Customizing a prebuilt agent and using Kapa retrieval inside your own application involve different responsibilities. Ask which settings your docs team can change directly and which require development or vendor help.
Inkeep: deeper implementation control
Inkeep separates its open-source agent framework from its Enterprise offering. The framework exposes model providers, fallbacks, and inherited settings. Its pricing documentation places managed ingestion, optimized retrieval, and dedicated engineering support within Enterprise.
Evaluate it when the project includes custom tools, agent orchestration, or deployment requirements beyond a ready-made docs assistant. Establish who will operate the resulting system. A free framework license does not include the running cost of a managed documentation service.
Mintlify and GitBook: AI within a publishing platform
If you already use one of these platforms, test its included AI before adding another service. Both also document ways to embed their assistant beyond a published docs site.
Mintlify Assistant is available on Pro and Enterprise. Its default models are selected by Mintlify. Bring your own model is an Enterprise contract option using your provider account. You can also customize response instructions, so customization is not exclusive to standalone assistants.
GitBook distinguishes Ask, available on Essential for answers from search, from full conversational Chat, available on Ultimate and Enterprise. Its assistant settings include custom instructions and suggested questions. Published GitBook docs include MCP even on Free. Mintlify also includes MCP on Starter, so a website chatbot subscription is not always necessary when MCP is your only requirement.
Compare authoring, hosting, versioning, and migration requirements alongside AI. The platform price pays for more than a chatbot.
Compare answer quality and configuration
Answer quality. Give each assistant the same documentation and ask the same questions. Include setup, troubleshooting, version-specific questions, and something your docs do not explain. Check whether the answers are correct, useful, and supported by the cited sources. An assistant should recognize when it lacks enough information to answer.
Configuration. Try adapting it to your product: change a source, adjust the instructions, and choose a model where supported. Run the questions again to see what changes. Check which settings your team can manage directly, which need vendor help, and which require a higher plan.
Use our evaluation guide to run the trial and the cost guide to estimate the budget.
To try Biel with your own documentation, start a 14-day trial.