GitHub Primer

Primer scores 6 of 8 and stands alone in eighth place, behind the 7 systems on 7 or 8. GitHub’s own pages and packages are the evidence, and GitHub has no tie to Simbolik. Its 2 lost points are the clearest single gap on the board: everything else is in place, and the docs are the part an agent cannot load.

The first 4 signs make the score out of 8: 2 points for a Yes, 1 for a Partly, none for a No. Typed props are rated beside them and left out of the score.

• Design tokens: Yes, 2 points. @primer/primitives 11.10.0 ships JSON and CSS variables, built from source design tokens that its guide says follow the W3C format. Proof: @primer/primitives on npm (opens in a new tab), checked November 8, 2026.
• Agent access: Yes, 2 points. @primer/mcp runs locally with npx @primer/mcp@latest and has 19 tools, among them component and design token lookups, lint_css and primer_coding_guidelines. Proof: GitHub Primer, MCP server (opens in a new tab), checked November 8, 2026.
• Docs: No, 0 points. https://primer.style/llms.txt answered 404, and adding .md to a page returns the same HTML page. There is no llms.txt and no Markdown copy. Proof: the research’s request to that address, checked November 8, 2026.
• Guidance: Yes, 2 points. The npm package includes DESIGN_TOKENS_GUIDE.md, written for language models with rules such as never using raw values, and the MCP page covers working with agents. The AGENTS.md files in Primer’s repositories are for contributors. Proof: Primer’s design token guide (opens in a new tab), checked November 8, 2026.
• Typed props: Yes, not scored. @primer/react 38.45.0 ships its type declarations. Proof: @primer/react on npm (opens in a new tab), checked November 8, 2026.

Product interfaces in GitHub’s style, in React or CSS, where agents must stay on design tokens and accessibility rules. The lint_css tool lets an agent check its own CSS against Primer before a person sees it.

• The server had a bug. Two of its component tools returned the home page for names of more than one word, until a fix in October 2026. Test the lookups your screens need.
• No license on the server’s npm page. The repository it is built in, primer/react, is under MIT, as are the main packages.
• Primer Brand is separate. GitHub’s brand design system, @primer/react-brand, has its own server, @primer/brand-mcp; this entry covers Primer for product UI.

The 2 missing points are among the cheapest to earn. An llms.txt at the root of primer.style, listing the component and foundation pages, and a Markdown copy of each page would do it, with no change to the code. Until GitHub adds them, connect your agents to the MCP server for docs, and say so in your AGENTS.md, so they do not scrape the site. How to raise your design system’s score uses Primer as its example, and the best AI-ready design systems, ranked show what 8 would mean for its place.