Sonar MCP

An MCP server exposing Solana network, wallet, transaction, and token-intelligence tools backed by the Helius RPC API. Built to plug directly into MCP-compatible clients such as Cursor.

Tools

Domain	Tool	Description
Network	get_slot	Current slot at a given commitment level
Network	get_epoch_info	Epoch progress: absolute slot, block height, index
Network	get_health	RPC node health check
Wallet	get_sol_balance	SOL balance for a wallet address
Wallet	get_token_accounts_by_owner	SPL token holdings for a wallet
Transactions	get_transaction	Full transaction detail by signature
Transactions	get_signatures_for_address	Recent transaction signatures for an address
Tokens	get_token_supply	Supply and decimals for an SPL token mint

Prerequisites

• Python 3.11+
• uv
• A Helius API key

Setup

git clone <your-repo-url> sonar-mcp
cd sonar-mcp
uv sync
cp .env.example .env

Edit .env:

HELIUS_API_KEY=your-key-here
SOLANA_NETWORK=devnet   # or mainnet

Running

Launch the MCP Inspector for local testing:

uv run mcp dev src/sonar_mcp/server.py

This opens a browser UI where each tool can be called directly against Helius before wiring the server into a client.

Using with Cursor

Add to .cursor/mcp.json (project-level) or your global Cursor MCP config:

{
  "mcpServers": {
    "sonar": {
      "command": "uv",
      "args": ["run", "--directory", "/absolute/path/to/sonar-mcp", "sonar-mcp"]
    }
  }
}

Reload MCP servers in Cursor and the 8 tools will appear under sonar.

Project structure

sonar-mcp/
├── .env.example
├── pyproject.toml
├── README.md
└── src/
    └── sonar_mcp/
        ├── instance.py      # shared MCPServer instance
        ├── server.py        # entrypoint, registers tool modules
        ├── config.py        # env + RPC URL
        ├── rpc_client.py    # shared Helius JSON-RPC POST helper
        └── tools/
            ├── network.py
            ├── wallet.py
            ├── transactions.py
            └── tokens.py

Notes

• Built on MCP Python SDK v2 (mcp.server.MCPServer). The old FastMCP class from mcp.server.fastmcp was renamed and moved in v2 — if you're reading examples elsewhere that import FastMCP, they're targeting SDK v1.
• All Solana RPC calls go through Helius directly; this server does not call the original Sonar FastAPI service.
• RpcError responses are returned as {"error": ...} payloads rather than raised, so tool calls degrade gracefully instead of crashing the MCP session.