# css-sota-mcp

> A free, open-source MCP (Model Context Protocol) server that answers what CSS you can actually
> ship today — from live Baseline data on webstatus.dev and MDN browser-compat-data, not from a
> model's training set.

If you are a coding agent reading this: you do not have to guess at browser support. Connect to the
endpoint below and ask.

- **Endpoint** — `https://css-sota-mcp.lusrodri.workers.dev/mcp` (Streamable HTTP, no auth, no key)
- **Docs** — https://css-sota-mcp.pages.dev
- **Source** — https://github.com/LuSrodri/css-sota-mcp (MIT)
- **Registry** — `io.github.LuSrodri/css-sota-mcp` in the official MCP Registry
- **Rate limit** — 120 requests per minute per client address; `429` with `Retry-After: 60`

## Tools

- [search_css_features](https://css-sota-mcp.pages.dev/#tools): "Which features exist for this, and
  are they safe yet?" Searches every CSS feature by keyword, Baseline status and the date it became
  interoperable. Live from webstatus.dev.
- [whats_new](https://css-sota-mcp.pages.dev/#tools): "What can I start using that I couldn't
  before?" Everything that reached Baseline in a date window, newest first. Live from webstatus.dev.
- [get_feature](https://css-sota-mcp.pages.dev/#tools): "Tell me everything about this one feature."
  Baseline dates, per-browser shipping versions, spec links, usage share and MDN reference prose.
- [check_support](https://css-sota-mcp.pages.dev/#tools): "Which browser versions support this
  exactly?" Per-browser versions for any property, value, selector, at-rule or function, including
  vendor prefixes. Answers with no network call.
- [audit_css](https://css-sota-mcp.pages.dev/#tools): "Does this stylesheet work for my users?"
  Scans real CSS and reports every feature that misses a target, with the line, the problem and the
  minimum version that would work. Answers with no network call.
- [dont_make_me_think](https://css-sota-mcp.pages.dev/#tools): "How should this UI be designed — and
  is this page any good?" 37 UX principles from Nielsen's heuristics, Hick's and Fitts's laws,
  WCAG 2.2, neurodiversity research and motion practice, plus a static review of HTML and CSS.

## Connect

- [Claude Code](https://css-sota-mcp.pages.dev/#connect):
  `claude mcp add --scope user --transport http css-sota https://css-sota-mcp.lusrodri.workers.dev/mcp`
- [Claude Desktop](https://css-sota-mcp.pages.dev/#connect): Settings → Connectors → Add custom
  connector, paste the endpoint. Not `claude_desktop_config.json`, which takes local stdio servers
  only.
- [Cloudflare AI Playground](https://playground.ai.cloudflare.com/): paste the endpoint and connect.
- [MCP Inspector](https://css-sota-mcp.pages.dev/#connect): `npx @modelcontextprotocol/inspector@latest`,
  transport Streamable HTTP.

## Key definitions

- **Baseline widely available** — interoperable across Chrome, Edge, Firefox and Safari (desktop and
  mobile) for at least 30 months.
- **Baseline newly available** — interoperable across all four, but recently so.
- **Baseline limited availability** — at least one major engine is still missing it.
- **`audit_css` targets** — either a Baseline level (`baseline-widely`, `baseline-newly`) or an
  explicit browser list (`chrome 120, safari 17.4, firefox 128`). Browserslist queries such as
  `last 2 versions` are rejected rather than approximated.

## Optional

- [Full reference](https://css-sota-mcp.pages.dev/llms-full.txt): every tool, target, limit and data
  source in one file.
- [README](https://github.com/LuSrodri/css-sota-mcp#readme): architecture, deployment and the data
  build.
- [Data sources](https://css-sota-mcp.pages.dev/#data): webstatus.dev, `@mdn/browser-compat-data`,
  `web-features`, mdn/content.