Tarandeep100/Polkadot_builder_mcp

Polkadot MCP Server (Next.js)

This project exposes an MCP server over HTTP (via mcp-handler) inside a Next.js app, mirroring the tool names from the Alchemy MCP server, but implemented for the Polkadot blockchain via polkadot.js.

Docs: https://polkadot.js.org/docs/

• Price methods are not natively supported via polkadot.js
• Balance and transfers are implemented using the Polkadot RPC and events.
• sendTransaction and swap forward to a generic agent wallet server via AGENT_WALLET_SERVER, making the agent integration generic (works with any agent server; test with Cursor).

Environment

• POLKADOT_WS_ENDPOINT (optional): defaults to wss://rpc.polkadot.io
• AGENT_WALLET_SERVER (optional): URL of a generic wallet agent server for signing/broadcasting

Run locally

pnpm install
pnpm dev
# then call POST http://localhost:3000/mcp with MCP payloads

MCP tools (kept same names)

• fetchTokensOwnedByMultichainAddresses: returns balances for given addresses on Polkadot
• fetchAddressTransactionHistory: scans recent blocks for balances.Transfer events for each address
• fetchTransfers: scans recent transfers for a single address (from/to)
• sendTransaction, swap: forwarded to AGENT_WALLET_SERVER
• Price/NFT tools: return not-supported errors

Cursor MCP config (HTTP)

Add to your MCP settings:

{
  "mcpServers": {
    "polkadot-builder": {
      "url": "http://localhost:3000/mcp",
      "capabilities": {}
    }
  }
}

Notes

• The scanning approach for history is best-effort and limited (recent N blocks). For full history/indexed NFT support, add a chain indexer or third-party API.

Polkadot Builder MCP

Enable users to design and execute workflow automations via MCP server endpoints, which are connected to the Polkadot ecosystem through RPCs or SDKs.