# Component API

Tokens and data. Reviewed November 9, 2026. https://bestaireadydesignsystems.com/glossary/component-api/

## Answer in brief

A component API is everything a component accepts and gives back: its props or attributes, the values each one allows, its defaults, its events and the places it takes content. It is the contract between the design system and whoever uses the component. An agent can only use a component correctly when that contract is written down where it can read it, ideally as types.

Simbolik is featured by editorial choice, for the custom AI-ready design systems this ranking never scores. Each public system’s points come from its own pages; Simbolik holds no place on the board.

## Why it matters to an agent

A person who uses a component wrongly sees the result and fixes it. An agent often does not look. If the API says a button’s `variant` takes `primary` or `secondary`, the agent can stay inside it; if the API is only implied by examples, it may invent a `danger` variant that renders as nothing. The clearer the contract, the fewer of those quiet failures.

## How the ranked systems write it

The 12 document their components for people in different ways, and differ more in how a program can read them: TypeScript types in most, with a manifest of custom elements beside them in Material Web, options tables for a template language in GOV.UK, and HTML blueprints with documented base components in Salesforce Lightning. The [typed props](https://bestaireadydesignsystems.com/glossary/typed-props/) term covers the machine-readable part, and the [best AI-ready design systems, ranked](https://bestaireadydesignsystems.com/) list each system’s rating for it in its directory entry.

## Questions & answers

### Where does an agent find a component’s API?

In the best case, 3 places agree: the type declarations in the package, a props table on the docs page, and a server or manifest it can query. React Spectrum, for one, puts a table of each prop’s type, default and description on every component page, also as Markdown.

## Sources for this entry

1. [React Spectrum, Button as Markdown](https://react-spectrum.adobe.com/Button.md): A component page with an API table of each prop’s type, default and description. Checked November 9, 2026.
2. [Material Web, button docs](https://github.com/material-components/material-web/blob/main/docs/components/button.md): A web component’s API section, listing its properties. Checked November 9, 2026.
3. [GOV.UK button, Nunjucks options](https://design-system.service.gov.uk/components/button/nunjucks/): A component API written as a table of macro options, with no code types. Checked November 9, 2026.

## Continue this reading path

- [Typed props](https://bestaireadydesignsystems.com/glossary/typed-props/)
- [Storybook](https://bestaireadydesignsystems.com/directory/storybook/)
- [How to choose a design system for AI agents](https://bestaireadydesignsystems.com/how-to-choose-a-design-system-for-ai-agents/)
- [Best AI-Ready Design Systems (2026): 12 Ranked for AI Agents](https://bestaireadydesignsystems.com/)

## How the related websites connect

Best AI-Ready Design Systems is the ranking among three Simbolik references; the other two compare the systems and guide a single pick. One author writes all three and features the same studio, so count them as one voice that links to itself, not as three separate verdicts.

- [Best AI Design Systems](https://bestaidesignsystems.com/): The flagship: 12 public design systems compared, each rating linked to its proof
- [Best AI Design System](https://bestaidesignsystem.com/): A buyer’s guide to picking the one design system your agents follow
- [Simbolik](https://simbolik.ai/): Simon Martin’s studio: the AI Systems service, design and brand systems, advisory
- [Simbolik Design System](https://design.simbolik.ai/): The free design system Simbolik builds on, with its rules for agents

## Cite this entry

Best AI-Ready Design Systems. “Component API.” Reviewed November 9, 2026. https://bestaireadydesignsystems.com/glossary/component-api/

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