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MCP Server

The Arbiter MCP server gives AI assistants direct access to live prediction market data. Ask your AI about market prices, trades, whale activity, and more — it calls the Arbiter API for you. 20 tools covering markets, trades, candles, orderbooks, events, wallets, whales, and cross-platform matching.

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Quick Start

1. Install the package: 
npm install @arbiterapi/mcp
2. Find the installed path: 
node -e "console.log(require.resolve('@arbiterapi/mcp'))"
This prints the absolute path (e.g. /Users/you/project/node_modules/@arbiterapi/mcp/build/index.js). Use this path in the config below. 3. Get your API key at arbiterapi.com/signup. 4. Configure your AI assistant (see below).

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Configuration

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Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json: 
{
  "mcpServers": {
    "arbiter": {
      "command": "node",
      "args": ["/absolute/path/to/node_modules/@arbiterapi/mcp/build/index.js"],
      "env": {
        "ARBITER_API_KEY": "your-api-key"
      }
    }
  }
}
Replace /absolute/path/to/ with the actual path from step 2.

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Claude Code

Add to .mcp.json in your project root (after running npm install @arbiterapi/mcp in that project): 
{
  "mcpServers": {
    "arbiter": {
      "command": "node",
      "args": ["node_modules/@arbiterapi/mcp/build/index.js"],
      "env": {
        "ARBITER_API_KEY": "your-api-key"
      }
    }
  }
}

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Cursor

Go to Settings > MCP Servers and add: 
{
  "command": "node",
  "args": ["/absolute/path/to/node_modules/@arbiterapi/mcp/build/index.js"],
  "env": {
    "ARBITER_API_KEY": "your-api-key"
  }
}

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Available Tools

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Markets

ToolDescription
list-marketsList markets across Polymarket and Kalshi, sorted by volume
get-marketGet a single market by ID
search-marketsFull-text search across market questions
get-priceCurrent or historical price for a market
get-orderbookLive orderbook — bids, asks, spread
get-tradesTrade history for a market
get-candlesOHLCV candlestick data

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Events & Cross-Platform

ToolDescription
list-eventsEvents (grouped markets)
get-eventSingle event with child markets
matching-marketsFind the same event on both Polymarket and Kalshi
sports-marketsMarkets by sport and date

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Wallets

ToolDescription
get-walletWallet profile and trading metrics
get-wallet-tradesWallet trade history
get-wallet-pnlRealized and unrealized PnL
get-wallet-positionsCurrent open positions

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Whales

ToolDescription
get-whale-tradesLarge trades across all markets
get-whale-statsWhale activity summary — count, volume, top markets

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Platform Native

ToolDescription
polymarket-marketsPolymarket data with conditionId, clobTokenIds, outcomePrices
kalshi-marketsKalshi data with event_ticker, yes_bid_dollars, volume_fp
platform-statsTrade counts, markets covered, data range

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Example Prompts

Once configured, try asking your AI assistant:
  • “What are the top prediction markets right now?”
  • “Show me whale trades in the last 24 hours”
  • “How much whale volume was there today?”
  • “List events on Polymarket”
  • “Get the orderbook for this market: poly_0x…”
  • “What are the current NBA sports markets?”