The MCP server is grounded's newest surface, shipped in v0.2.0. grounded-mcp runs on the official Python MCP SDK over stdio and exposes the retrieval stack as three protocol tools. retrieve is the raw path: the top-k chunks for a question, each with its source, heading and cosine score, with the abstention floor reported alongside for context. answer_evidence is the governed one: it returns an evidence set only when the best hit clears the measured 0.68 floor, and otherwise an explicit abstention carrying the floor and the raw best score, so the calling agent is told the corpus cannot support an answer rather than left to guess one. graph_paths returns real multi-hop traversals from the embedded KuzuDB graph, and against an unbuilt graph it raises an error naming the remedy, because a missing graph must never read as no relationship exists.
The point of the surface is who can now call it. MCP is the protocol agents actually use, so Claude Code, Claude Desktop, Cursor, or anything else that speaks it can mount grounded as a tool and inherit the gate for free. The abstention travels as data, not as a refusal buried in prose: an agent that receives abstained: true with the floor and the best score can report the gap honestly instead of papering over it. And the whole surface is keyless, because no tool touches a generator; what crosses the wire is evidence and verdicts, never invented sentences.
Verification runs at the protocol level, not the function level. Eight tests boot a real server subprocess and drive it over stdio, initialize, list the tools, call each one, on the same fake-embedding seam the rest of the suite uses, so they run offline in CI. The release was then checked live from a client: an in-corpus question came back cited with a best score of 0.78, and an out-of-corpus probe came back as an explicit abstention at 0.47, below the 0.68 floor. The same oath as the rest of grounded, now sworn over a wire any agent can reach.