A frontier model already knows Atomic Design and the WCAG criteria; what it cannot know is that MCP Apps moved a field name last quarter. This base is built around that gap — dated, cited, primary-source extracts of the specs that changed recently — and the relevance floor means it returns nothing rather than something adjacent when a topic is genuinely uncovered.
A hosted MCP server over a curated knowledge base of design systems material: W3C standards, WCAG 2.2, ARIA practices, the major design systems, and the agent-interface protocols that move faster than model training does. It runs on Cloudflare Workers with vector search backed by Supabase pgvector, and a keyword path that keeps working when embeddings are not available.
- Semantic search across the whole knowledge base, filterable by category and tags — `search_design_knowledge`
- Chunk-level search when the answer is a passage rather than a document — `search_chunks`
- Browsing by category across components, tokens, patterns, guidelines, workflows and general — `browse_by_category`
- Tag discovery and tag-scoped browsing for exploring what is covered — `get_all_tags`, `browse_by_tag`
- A relevance floor built on IDF-weighted scoring, so a topic the base does not cover returns nothing rather than confident adjacent material
- Source reliability flags on every answer — Primary, Authoritative, Reference, Example or Community
- Coverage of the fast-moving specs: A2UI v1.0, MCP Apps / SEP-1865 with its `ui://` resources and `ui/` method namespace, AG-UI events, the OpenAI Apps SDK to MCP Apps field migration map, component contracts, and the AGENTS.md / SKILL.md layer
- Depth on the major systems — Carbon, Polaris, Atlassian, Material 3, Fluent, Spectrum, Nord, Mantine, shadcn/ui, Radix, Untitled UI — covering guidance and token architecture rather than prop tables
Nothing. It is a public endpoint at `https://design-systems-mcp.southleft.com/mcp`, added as a custom connector or a one-line `claude mcp add --transport http`, and works with any MCP client that supports remote servers. Running your own copy means a Cloudflare Workers deployment plus Supabase with pgvector, and either Cloudflare Workers AI for embeddings or an OpenAI key. Licensed MIT.
One command — claude mcp add --transport http design-systems https://design-systems-mcp.southleft.com/mcp