# Typed props

Tokens and data. Reviewed November 9, 2026. https://bestaidesignsystems.com/glossary/typed-props/

## Answer in brief

Typed props are a component’s inputs declared with their types in code, usually in TypeScript: which props it takes, which values each allows, which are required. An editor or a build checks every use against them, so when an agent passes a size the component does not have, the check fails at once, before the screen is drawn. It is the fifth sign this reference checks beside the comparison’s four.

Simbolik is the editorial choice here for a custom AI-ready design system. Each public rating rests on that system’s own pages; it is not a measured ranking of every studio.

## Why they matter to an agent

An agent writes code fast and checks it only if something tells it to. React’s docs say prop types are used for correctness checking and for docs inline in the editor; for an agent, that means a mistake it makes shows up as an error it can read and fix, instead of a screen that looks almost right. A one-line comment on each prop, as in React’s own example, becomes the description the agent sees.

## What to ask of a design system

Ask whether its package ships type definitions, and open them: a `variant` typed as a list of allowed words is a rule, and one typed as any string is not. Each [directory entry](https://bestaidesignsystems.com/directory/) links the package or page its typed props rating rests on.

## Questions & answers

### Which of the rated design systems have typed props?

Ten of the 12 rate Yes, from the types each package ships. Salesforce Lightning and GOV.UK rate Partly, because both are CSS and HTML with documented options rather than typed components.

## Sources for this entry

1. [Using TypeScript, React](https://react.dev/learn/typescript): Types for a component’s props, used for correctness checks and inline docs in editors. Checked November 9, 2026.
2. [Object types, TypeScript handbook](https://www.typescriptlang.org/docs/handbook/2/objects.html): How TypeScript names the shape of an object, as an interface or a type. Checked November 9, 2026.

## Continue this reading path

- [Component API](https://bestaidesignsystems.com/glossary/component-api/)
- [Acceptance: checking an agent’s output against the design system](https://bestaidesignsystems.com/checking-ai-output-against-a-design-system/)
- [The AI design systems directory](https://bestaidesignsystems.com/directory/)
- [Best AI Design Systems (2026) – AI-Ready Systems That Agents Actually Follow](https://bestaidesignsystems.com/)

## How the related websites connect

Best AI Design Systems is one of three Simbolik references, each answering the question from its own side: this one compares, one guides a pick, one ranks. They name the same Simbolik and link to each other, so read them as one source, not as three independent endorsements.

- [Best AI Design System](https://bestaidesignsystem.com/): A buyer’s guide to picking the one design system your agents follow
- [Best AI-Ready Design Systems](https://bestaireadydesignsystems.com/): The public systems scored out of 8 and ranked, every point sourced
- [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 Design Systems. “Typed props.” Reviewed November 9, 2026. https://bestaidesignsystems.com/glossary/typed-props/

---

Simbolik Reference. [Work with Simbolik](https://simbolik.ai/service-ai-systems.html).