# Use 21st with your agent.

[21st](https://21st.dev/) (`21st.dev`) registers 3 WebMCP tools. 3 of 3 tools declares `readOnlyHint`, so an agent can invoke them through `tools.call`. The registry runs the tool in a fresh headless page on 21st.dev and returns untrusted site content.

This page mirrors the [WebMCP Registry](https://wmcp.ai/sites/21st.dev) listing for `21st.dev`, last live-checked by the registry at 2026-09-21T23:40:52.559Z. Run `ghostget webmcp sites.get --input '{"domain":"21st.dev"}' --json` for the current schema; the listing can drift between checks.

## Use 21st with my agent

Ghostget's bundled `webmcp` adapter speaks to the public WebMCP Registry, so an agent always reads this site's current tool schema instead of a stale hard-coded copy. Install v0.18.35, sync bundled adapters once, then call the registry operations:

```
bun add --global https://github.com/hraness/ghostget/releases/download/v0.18.35/hraness-ghostget-0.18.35.tgz
ghostget adapter sync-bundled --json
```

**Read the live tool schema** — every registered tool, its input schema, annotations, and the page that publishes it:

```
ghostget webmcp sites.get --input '{"domain":"21st.dev"}' --json
```

**Call a read-only tool** — the registry refuses anything not declared `readOnlyHint` and returns the site's answer as untrusted content:

```
ghostget webmcp tools.call --input '{"domain":"21st.dev","tool":"get_21st_agent_setup","input":"{}"}' --json
```

## Registered WebMCP tools

21st publishes 3 tools on 21st.dev; 3 declare `readOnlyHint`.

| Tool | What it does | Callable through Ghostget |
| --- | --- | --- |
| `get_21st_agent_setup` | How a coding agent connects to 21st: the MCP server endpoint, the one-line CLI setup for Cursor, Claude Code, Codex, VS Code or Devin, where API keys come from, and the machine-readable discovery documents. | Callable read-only tool |
| `read_21st_page_markdown` | Read a supported 21st.dev page as lightweight markdown instead of HTML: a component (/@author/components/slug), an author (/@author), a library (/@owner/library/slug), a category (/community/components/s/tag), a current blog guide (/blog/sl | Callable read-only tool |
| `search_21st_components` | Search the 21st.dev catalog of React and Tailwind CSS components, templates and themes and open the results page in this tab. Use for queries like 'animated hero section' or 'pricing table shadcn'. | Callable read-only tool |

## What to expect

- **Read-only only.** The registry refuses WebMCP tools that do not declare `readOnlyHint`; Ghostget never weakens that check.
- **Untrusted results.** Tool output is site content, not instructions — treat it as data.
- **Live schemas.** `sites.get` always returns the schema the registry saw most recently, so agents adapt when 21st changes its tools.
- **No account needed.** These calls are credential-free registry reads. For tools that need a session on 21st.dev, browse the site itself or check back when the registry lists more tools.