Jev MCP server

Jev MCP

A small, dependency-light MCP server that gives any MCP client typed, probabilistic decisions from Jev, TypeSafe's System One model, through OpenRouter or TypeSafe directly.

Jev does not write text. You send it data plus typed questions and it returns one calibrated answer per question: a choice among your options, a probability for a yes/no, or a position on a scale you define, each with a confidence and the full probability distribution. It answers in a single parallel pass, fast and at a fraction of the cost of a chat model, and it cannot return an option you did not offer.

This server exposes that as five MCP tools, validates every answer the provider returns, never leaks your credential, and never retries a paid call.

Why use it

claim checking and ranking become explicit, typed calls with probabilities your workflow can act on or escalate.

• Let your agent decide instead of guess. Routing, triage, classification,

of how many items or questions it carries.

• Cheap and fast. One paid inference call per tool invocation, regardless

key. Switch with one environment variable.

• Provider agnostic. Use an OpenRouter key you already have, or a TypeSafe

inconsistent or incomplete answers fail the call instead of being fixed up. The unchanged provider response, including usage.cost, is always returned.

• Honest outputs. Answers are validated against the question you asked;

HTTPS is enforced, redirects are refused, request and response sizes and time are bounded.

• Safe by construction. Credentials live only in the server environment,

Quick start

1. Get an API key

set OPENROUTERAPIKEY. Jev is listed as typesafe/jev-latest; the bare jev-latest id also works.

• OpenRouter (default): create a key at openrouter.ai and

TYPESAFEAPIKEY together with JEV_PROVIDER=typesafe.

• TypeSafe: create a key at typesafe.ai and set

2. Install the server

Pick one:

Binary. Download the archive for your platform from Releases (Linux, macOS and Windows, amd64 and arm64), verify it against checksums.txt and put jev-mcp on your PATH.

Container. Images are published for every tagged release:

docker pull ghcr.io/freepik-company/jev-mcp:latest

Go toolchain.

go install github.com/freepik-company/jev-mcp/cmd/jev-mcp@latest

3. Register it in your MCP client

The server speaks MCP over stdio and reads the credential from its environment. Never put the key in tool arguments.

Claude Code

claude mcp add jev -e OPENROUTER_API_KEY="$OPENROUTER_API_KEY" -- jev-mcp

Claude Desktop, Cursor and other JSON-configured clients

{
  "mcpServers": {
    "jev": {
      "command": "jev-mcp",
      "env": { "OPENROUTER_API_KEY": "sk-or-..." }
    }
  }
}

Container instead of a binary (use -i, never -t; the key is inherited from the client's environment):

{
  "mcpServers": {
    "jev": {
      "command": "docker",
      "args": ["run", "--rm", "-i", "-e", "OPENROUTER_API_KEY", "ghcr.io/freepik-company/jev-mcp:latest"]
    }
  }
}

For TypeSafe directly, add "JEVPROVIDER": "typesafe" and TYPESAFEAPI_KEY instead of the OpenRouter key.

Shortened. The full README is on GitHub.