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guessmarket-mcp

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Decentralized prediction market MCP server. 17 tools. Trade, provide liquidity, and claim winnings on-chain.

0 stars TypeScriptOthers Updated Mar 14, 2026

Documentation

GuessMarket MCP Server

MCP server for GuessMarket prediction markets. Gives AI agents full access to discover markets, analyze prices, check on-chain balances and positions, build trading transactions, and get smart contract ABIs.

Live on 5 EVM chains: Ethereum, Base, Polygon, BSC, and PulseChain.

Tools

Read-Only (API)

ToolDescription
`list_markets`List prediction markets with filters for status and chain
`get_market`Get detailed market info: question, YES/NO odds, volume, liquidity, end time
`get_market_history`Get timestamped price history for trend analysis
`get_networks`Get all supported chains with contract addresses
`get_portfolio`Get a wallet's trading activity across all markets
`get_abi`Get smart contract ABI for custom integrations

Read-Only (On-Chain)

ToolDescription
`get_balance`Get a wallet's stablecoin (USDC/USDT) balance on any chain
`get_allowance`Check how much stablecoin a market is approved to spend from a wallet
`get_position`Get a wallet's YES shares, NO shares, and LP tokens on a specific market

These tools read directly from the blockchain via public RPC endpoints. No API keys required.

Transaction Builders

All transaction builders return unsigned EVM transaction objects. Sign with your wallet and broadcast to the chain. Amounts are human-readable (e.g. `"10.5"`) and automatically converted to the correct decimals per chain (6 for USDC, 18 for BSC USDT).

ToolDescriptionKey Parameters
`build_approve_tx`Approve stablecoin spending for a market`market_address`, `amount` (or `"max"` for unlimited), `chain_id`
`build_buy_shares_tx`Buy YES or NO outcome shares`market_address`, `outcome`, `amount`, `chain_id`, `min_shares` (slippage)
`build_sell_shares_tx`Sell YES or NO outcome shares`market_address`, `outcome`, `shares`, `chain_id`, `min_usdc` (slippage)
`build_add_liquidity_tx`Add stablecoin liquidity, receive LP tokens`market_address`, `amount`, `chain_id`
`build_remove_liquidity_tx`Burn LP tokens, receive stablecoin back`market_address`, `lp_tokens`, `chain_id`
`build_claim_winnings_tx`Claim winnings from a resolved market`market_address`, `chain_id`
`build_create_market_tx`Create a new prediction market`question`, `end_time` (unix timestamp), `chain_id`
`build_buy_with_approval_tx`Approve + buy in one call (returns 2 ordered transactions)`market_address`, `outcome`, `amount`, `chain_id`, `min_shares` (slippage)

Slippage Protection

`build_buy_shares_tx` and `build_sell_shares_tx` accept optional slippage parameters (`min_shares` and `min_usdc`). When set to `0` (default), the server returns a warning. Set a minimum to protect against front-running.

Trading Flow

Buy Shares

code
1. list_markets               → Find a market to trade
2. get_market                  → Check current odds and liquidity
3. get_balance                 → Check your stablecoin balance
4. get_allowance               → Check if approval is needed
5. build_approve_tx            → Approve stablecoin spending (if needed)
6. build_buy_shares_tx         → Buy YES or NO shares
7. Sign and broadcast transactions with your wallet
8. get_position                → Verify your shares

Or combine steps 5-6 with `build_buy_with_approval_tx` which returns both transactions in order.

Sell Shares

code
1. get_position                → Check your share holdings
2. build_sell_shares_tx        → Sell shares back to the market
3. Sign and broadcast the transaction
4. get_balance                 → Verify stablecoin received

Provide Liquidity

code
1. build_approve_tx            → Approve stablecoin spending
2. build_add_liquidity_tx      → Deposit stablecoin, receive LP tokens
3. get_position                → Verify LP tokens received
4. build_remove_liquidity_tx   → Later: burn LP tokens to withdraw

Create a Market

code
1. build_create_market_tx      → Deploy a new prediction market
2. Sign and broadcast — the new market address is in the tx receipt

Transaction Response Format

json
{
  "transaction": {
    "to": "0x...",
    "data": "0x...",
    "chainId": 8453,
    "value": "0x0"
  },
  "description": "Buy YES shares for 10 USDC on market 0x... (Base Mainnet)",
  "meta": {
    "chain": "Base Mainnet",
    "stablecoin": "USDC",
    "outcome": "YES",
    "function": "buyShares(uint8,uint256,uint256)"
  },
  "warnings": []
}

Quickstart

Claude Desktop

Add to your `claude_desktop_config.json`:

json
{
  "mcpServers": {
    "guessmarket": {
      "command": "npx",
      "args": ["-y", "guessmarket-mcp"]
    }
  }
}

Claude Code

Add to your project with the CLI:

bash
claude mcp add guessmarket -- npx -y guessmarket-mcp

Or add to `.mcp.json` in your project root:

json
{
  "mcpServers": {
    "guessmarket": {
      "command": "npx",
      "args": ["-y", "guessmarket-mcp"]
    }
  }
}

VS Code

Add to your VS Code settings or `.vscode/mcp.json`:

json
{
  "mcp": {
    "servers": {
      "guessmarket": {
        "command": "npx",
        "args": ["-y", "guessmarket-mcp"]
      }
    }
  }
}

Supported Chains

ChainChain IDStablecoin
Ethereum1USDC (6 decimals)
Base8453USDC (6 decimals)
Polygon137USDC (6 decimals)
BSC56USDT (18 decimals)
PulseChain369USDC (6 decimals)

Configuration

No API keys required — the server uses the public GuessMarket REST API.

Custom API URL

By default the server connects to `https://guessmarket.com/api/guessmarket/v1`. Override with an environment variable:

json
{
  "mcpServers": {
    "guessmarket": {
      "command": "npx",
      "args": ["-y", "guessmarket-mcp"],
      "env": {
        "GUESSMARKET_API_URL": "https://your-instance.com/api/guessmarket/v1"
      }
    }
  }
}

Architecture

code
AI Agent    MCP Server    GuessMarket REST API (market data)
   |                  |
   |                  └───────>  Public RPCs (on-chain reads)
   |                                    |
   |                              5 EVM Chains
   |                          (Ethereum, Base, Polygon,
   |                             BSC, PulseChain)
   |
   └── Signs & broadcasts unsigned transactions on-chain

The MCP server provides market data (via REST API), reads on-chain state (via public RPC endpoints), and builds unsigned transactions (via local ABI encoding). The agent signs transactions with its own wallet and broadcasts directly to the blockchain.

Requirements

  • Node.js 18 or later (uses native `fetch`)

Development

bash
npm install
npm run build
node build/index.js

License

MIT

Frequently asked questions

What is guessmarket-mcp?

guessmarket-mcp is Decentralized prediction market MCP server. 17 tools. Trade, provide liquidity, and claim winnings on-chain.

How do I install guessmarket-mcp?

Open the GitHub repository and follow its README. Most MCP servers are added to your client's MCP config, then called by your agent.

Is guessmarket-mcp open source?

Yes — it is hosted on GitHub at https://github.com/hifriendbot/guessmarket-mcp.

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