# Oracle3 prediction-market arbitrage checks (MCP server)

> Oracle3 prediction-market arbitrage checks is an MCP server that adds finance tools to AI assistants such as Claude Desktop, Claude Code and Cursor. Kalshi and Polymarket data, venue fees, no-arbitrage checks and paper execution for AI agents. It has 341 GitHub stars, is released under the Apache-2.0 license and runs locally with uvx oracle3.

Oracle3 is an open-source trading engine and MCP server for prediction markets. It maps the logical relations between event contracts, finds prices that break the axioms of probability after each venue's fees, and trades them live on Kalshi, Polymarket and Solana, or on paper, under pre-trade risk limits.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/YichengYang-Ethan/oracle3-prediction-market-agent |
| GitHub stars | 341 |
| License | Apache-2.0 |
| Language | Python |
| Transport | stdio |
| Packages | pypi: oracle3 |
| Remote URL | none |
| Needs API key | no |
| Official | no |
| Works with | Claude Desktop, Claude Code, Cursor, VS Code |
| Category | Finance |
| Latest release | v1.2.2 (Sep 30, 2026) |
| Last commit | Oct 7, 2026 |
| MCP registry name | io.github.YichengYang-Ethan/oracle3 |

## Install

### Claude Desktop (claude_desktop_config.json)

```json
{
  "mcpServers": {
    "oracle3-prediction-market-arbitrage-checks": {
      "command": "uvx",
      "args": [
        "oracle3"
      ],
      "env": {
        "ORACLE3_MCP_LEDGER": "your-value"
      }
    }
  }
}
```

Settings > Developer > Edit Config. macOS: ~/Library/Application Support/Claude/, Windows: %APPDATA%\Claude\. Restart Claude Desktop afterwards.

### Claude Code

```sh
claude mcp add --env ORACLE3_MCP_LEDGER=your-value --transport stdio oracle3-prediction-market-arbitrage-checks -- uvx oracle3
```

### Cursor (.cursor/mcp.json)

```json
{
  "mcpServers": {
    "oracle3-prediction-market-arbitrage-checks": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "oracle3"
      ],
      "env": {
        "ORACLE3_MCP_LEDGER": "your-value"
      }
    }
  }
}
```

Project file; use ~/.cursor/mcp.json to enable it in every project.

### VS Code (.vscode/mcp.json)

```json
{
  "servers": {
    "oracle3-prediction-market-arbitrage-checks": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "oracle3"
      ],
      "env": {
        "ORACLE3_MCP_LEDGER": "your-value"
      }
    }
  }
}
```

Config formats checked against the official docs on 2026-10-07.

## Environment variables

- `ORACLE3_MCP_LEDGER`: Path of the local paper-trading ledger (default ~/.oracle3/mcppaperledger.json)

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