Arena MCP server

# install the binary (the agent prompt and the hook call arena)
npm install -g arena-prediction-cli
arena login

# or try it without installing (arena is not added to your PATH)
npx arena-prediction-cli login

One sign-in is enough. Your agent and the MCP server act with that login. For an agent, install the binary, because the prompt and the hook call arena directly.

Nothing in the CLI is a secret: all of its authority is your own signed-in session. There is nothing else to install for agent use. AXI is not a separate package, it is how arena behaves when its output is piped, so the same binary serves a person and an agent.

Claude Code

claude mcp add arena -- npx -y arena-mcp-server

Cursor and VS Code

Run arena login once first: the server uses the CLI’s stored sign-in. Then one click adds the server to Cursor or VS Code.

Cursor reads the same mcpServers block from ~/.cursor/mcp.json, or from .cursor/mcp.json inside one project. VS Code reads a servers block from .vscode/mcp.json in a workspace.

{
  "mcpServers": {
    "arena": {
      "command": "npx",
      "args": ["-y", "arena-mcp-server"]
    }
  }
}

{
  "servers": {
    "arena": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "arena-mcp-server"]
    }
  }
}

Claude Desktop and other clients

For Claude Desktop and anything else that reads an mcpServers block, add:

{
  "mcpServers": {
    "arena": {
      "command": "npx",
      "args": ["-y", "arena-mcp-server"]
    }
  }
}

Environment

Tools

Sixteen tools register by default. Six work signed out: the two records tools, resolve_market, and the three universal-ticker lookups get_instrument, get_game and list_games. The other ten act on the account that ran arena login. The five trade tools register only when ARENA_MCP_ALLOW_TRADE=1 is set, and every one of them that changes the account also needs confirm: true in the call.

Trust

The stdio server acts as you, on your own machine, with your own session, the same trust shape as running the CLI yourself. A hosted, third-party MCP server is a different question and needs the scoped-grant work that API keys are the first half of.

The server runs on your machine. It reads only its own settings and your stored sign-in. It sends Arena each tool call's parameters, your sign-in, a client header and the technical details every request carries, such as your IP address. It contains no analytics or telemetry.

Specifications

GET https://arena-predictions.com/api/v1/openapi.json is the OpenAPI 3.1 document for the live endpoints; /llms.txt is the short version for a language model. The CLI and the MCP server call the same backends the website does, through arena-core. There is no separate SDK for the HTTP API.