jev-in-mcp

Jev lives inside an MCP relay. To the agent it is one MCP server; to the user's MCP servers it is a client. Every tool passes through unchanged, every server gets one extra tool, <server>__use_jev, and there is one global use_jev over all servers; each hands a goal to TypeSafe Jev: Jev picks the tool calls, the calling model supplies any text that has to be written, and the relay executes. Built on jev-dev-kit.

client (LLM) ──MCP──► jev-in-mcp ──MCP──► github, filesystem, browser, ...
                          ├── <server>__use_jev(goal): Jev runs that server's tools in a loop
                          └── use_jev(goal): the same over every server (server chosen first, then the tool)

Install

Node 20+. Three commands, then restart your MCP client.

npx jev-in-mcp setup     # a local page to store the Jev API key (OpenRouter or TypeSafe); nothing goes through a chat
npx jev-in-mcp import    # copies the mcpServers entries of Claude Code, Cursor, Windsurf and Claude Desktop into jev-in-mcp's config
npx jev-in-mcp status    # what is configured, which servers connect, how many tools each has

Then replace the servers in your client's config with one entry:

{ "mcpServers": { "jev": { "command": "npx", "args": ["-y", "jev-in-mcp"] } } }

Config lives in ~/.config/jev-in-mcp/config.json (or $JEV_IN_MCP_HOME); the key in credentials.json next to it (mode 600), or in JEV_API_KEY. Not on npm yet: install from GitHub with npm install -g github:chy4pro/jev-in-mcp and use jev-in-mcp in place of npx jev-in-mcp.

{
  "servers": {
    "github": { "command": "npx", "args": ["-y", "@modelcontextprotocol/server-github"], "env": { "GITHUB_TOKEN": "..." },
                "purpose": "Issues, pull requests and files on GitHub",
                "jev": { "deny": ["delete_repository"], "describe": { "create_issue": "Opens a new issue with the given title and body; returns its number." } } },
    "notes":  { "url": "http://localhost:8080/mcp" }
  },
  "jev": { "provider": "openrouter", "model": "typesafe/jev-1.13" },
  "use_jev": { "global": true, "max_steps": 20, "result_chars": 800 }
}

Related MCP server: MetaMCP

What the client sees

• <server>__<tool>: every downstream tool, passed through unchanged.

• <server>__use_jev(goal, max_steps?, pause_after?, session?, input?): Jev runs that server's tools toward the goal, one decision per step (~300 ms), and returns the status, the trace and every call made. When a value must be written rather than chosen (a search query, a note's text), the call returns status: "needs_input" with the field and a session; the model calls the same tool again with session and input and the run continues. Where the client supports MCP sampling, the relay asks the model inside the call instead and nothing is interrupted.

• use_jev(goal, servers?, ...): the same over every server. Jev picks the server first, then the tool, in one request.

• jev_status(): servers, key status, and which tools each use_jev may use.

Tools with a required parameter Jev cannot express (objects, arrays) are not offered to Jev; deny keeps destructive tools away from it; describe replaces a tool's sentence with what actually happens when it is called, which is where the quality of a server's use_jev is decided.

Status

0.1.1. Verified live against the reference filesystem server with real Jev and DeepSeek as the calling model, in both the needs_input and the sampling path: 6/6 tasks, one Jev decision each, 4 to 10 seconds per task including the model writing values. Details in docs/live-run-2026-09-20.md; the same 6/6 through Vercel AI Gateway in docs/live-run-2026-09-22-vercel.md. Other servers have not been tried yet.

Relation to other projects

• jev-dev-kit: the framework this is built on. use_jev is its runLoop; the relay supplies candidates (tools), text (the calling model) and actions (tool calls).

• jev-for-chrome: the Chrome extension; a browser becomes one more downstream server once it exposes an MCP endpoint.

• jiawei686/jev-ultrafast-mcp: Jev driving a browser behind one MCP tool. jev-in-mcp is not browser-specific: any MCP server gets a use_jev.

• abhishekashokvkumar/jev-mcp-dispatcher: Jev picking one tool call from one sentence. jev-in-mcp runs multi-step loops and lets the calling model write the values Jev cannot choose.

Roadmap

1. Relay with pass-through tools, per-server use_jev with the needs_input path, setup page for the key.

2. Sampling path where the client supports it; config import from clients.

3. Per-tool description overrides and a small eval set per common server.

4. Options supplied by the model: the calling model writes a few fixed programs (scripts, recipes) and registers them as candidates, so Jev chooses among them and the relay runs them. Not designed yet; the open questions are where such programs live, how they are described to Jev, and how they are kept safe.

License

MIT