onchain-mcp

A Model Context Protocol (MCP) server that gives any MCP client — Claude Desktop, Claude Code, Cursor, etc. — live, read-only access to Solana on-chain data. Ask natural-language questions like "what SPL tokens does this wallet hold?" or "what's the USD price of this mint?" and the model answers from real Solana mainnet RPC + Jupiter, no API key required.

Tools

Tool	What it does
get_sol_balance(address)	Native SOL balance of an account
get_token_holdings(address)	Non-zero SPL token balances of a wallet
get_token_price(mint)	USD price of a token mint (via Jupiter)
get_transaction(signature)	Parsed transaction summary (slot, fee, logs, success)
get_account_info(address)	Owner program, lamports, executable flag
get_token_supply(mint)	Total on-chain supply of a token mint
get_recent_signatures(address)	Recent transaction signatures for an account
get_epoch_info()	Current epoch / slot / block height / progress

All endpoints are public. Point at a private RPC by setting SOLANA_RPC_URL (and optionally JUPITER_PRICE_API).

Run

# Run the server over stdio (what an MCP client launches):
uv run --with "mcp>=1.2" --with httpx onchain_mcp.py

Use with Claude Desktop / Claude Code

Add to your MCP config (claude_desktop_config.json or .mcp.json):

{
  "mcpServers": {
    "onchain": {
      "command": "uv",
      "args": ["run", "--with", "mcp>=1.2", "--with", "httpx",
               "/absolute/path/to/onchain-mcp/onchain_mcp.py"]
    }
  }
}

Then ask, e.g.: "Using the onchain tools, what's the USDC price and how much SOL does <address> hold?"

Test

Live smoke tests against mainnet (asserts USDC ≈ $1, the SPL Token program is executable, balance/holdings shapes):

uv run --python 3.12 --with "mcp>=1.2" --with httpx \
  --with pytest --with pytest-asyncio pytest test_onchain_mcp.py -q

Notes

• Read-only: the server never signs or sends transactions — it only queries public chain state, so it is safe to expose to an LLM.
• Default RPC is api.mainnet-beta.solana.com (rate-limited); use a dedicated RPC for heavy use.

License

MIT