ENGINEERING · 2026-08-06 · 5 min read
Agent tooling: MCP + RAG over the design authority
Coding agents should not have to load the whole design authority into context to use it. A local MCP server now exposes search, get_doc, list_docs, lookup_token, search_tokens, and get_context over the Markdown and tokens.css.
Retrieval is lexical BM25 — deterministic, pure-stdlib, no model, no network, no API key. It matches the zero-cost, open-source ethos, and it keeps agents grounded in exact token values instead of whatever they remembered from last week.
The design authority is now something an agent can query, not just something it was supposed to have read. Drop the server into opencode.json and the agent can pull the spacing scale mid-edit without a web search.