stellar-mcp-x402

StellarMCP

Data Merchant for the Agent Economy

MCP server giving AI agents access to Stellar blockchain data — accounts, DEX orderbooks, transactions, trade history, asset metadata, and network status — with every tool call monetized via x402 micropayments settled on Stellar.

Built for the Stellar Hacks: Agents hackathon.

Features

• 16 MCP tools querying the Stellar Horizon REST API
• PriceService with VWAP, OHLC history, and oracle abstraction layer
• x402 micropayments on Stellar — agents pay per call in USDC
• Dual transport — stdio for MCP clients, HTTP REST for x402-gated access
• Earn/spend demo — agent earns USDC selling data, spends USDC on external services
• OpenClaw registered — permissionless agent discovery via GET /skill.md
• Zero dependencies on @stellar/stellar-sdk — raw fetch to Horizon

Quick Start

MCP Client (stdio — free, local)

npx stellar-mcp-x402

Or add to your MCP client config:

{
  "mcpServers": {
    "stellarmcp": {
      "command": "npx",
      "args": ["stellar-mcp-x402"],
      "env": {
        "STELLAR_NETWORK": "testnet"
      }
    }
  }
}

HTTP Server (x402-monetized)

git clone https://github.com/siriuslattice/stellarmcp.git
cd stellarmcp
pnpm install
cp .env.example .env
# Edit .env with your Stellar testnet wallet and OZ facilitator key
TRANSPORT=http pnpm start

Then query:

# Free endpoint
curl http://localhost:4021/tools/getNetworkStatus

# Paid endpoint (requires x402 payment header)
curl http://localhost:4021/tools/getAccount?accountId=GAAZI4TCR3TY5OJHCTJC2A4QSY6CJWJH5IAJTGKIN2ER7LBNVKOCCWN7

# View pricing
curl http://localhost:4021/pricing

Tools

Horizon Data Tools

Tool	Description	Price
getAccount	Account balances, thresholds, signers	$0.001
getTransactions	Recent transactions for an account	$0.001
getPayments	Recent payments for an account	$0.001
getOrderbook	DEX orderbook with spread and midprice	$0.002
getTradeAggregations	OHLC candle data for a trading pair	$0.002
getAssetInfo	Asset metadata, supply, flags	$0.001
getNetworkStatus	Network health and protocol version	Free
getLedger	Ledger details by sequence number	$0.001
getEffects	Account effects (balance changes, trades, etc.)	$0.001
getOffers	Open DEX offers for an account	$0.001
getOperations	All operations for an account	$0.001
getLiquidityPools	Stellar AMM liquidity pools	$0.002
getClaimableBalances	Claimable balances by claimant or asset	$0.001

Price Tools

Tool	Description	Price
getPrice	Current price for any Stellar asset pair	$0.002
getPriceHistory	OHLC price history with VWAP	$0.002
getVWAP	Volume-weighted average price	$0.002

The price tools are powered by PriceService, which aggregates data from the Stellar SDEX via trade aggregations. The oracle abstraction layer supports multiple price sources (SDEX, Reflector) with source attribution.

Asset Format

Type	Format	Example
Native	XLM	XLM
Classic	CODE:ISSUER	USDC:GA5ZSEJYB37JRC5AVCIA5MOP4RHTM335X2KGX3IHOJAPP5RE34K4KZVN

Agent Demo

The earn/spend loop demonstrates the full agent economy:

# Terminal 1: Start the x402 HTTP server (earn side)
TRANSPORT=http pnpm start

# Terminal 2: Start a mock external x402 service (spend side)
pnpm demo:service

# Terminal 3: Run the agent demo
pnpm demo

The agent:

• Earns USDC by receiving x402 payments from clients querying Stellar data
• Spends USDC by paying external x402 services to enrich its outputs

Development

pnpm install
pnpm typecheck    # Type check (zero errors required)
pnpm test         # Run unit tests
pnpm build        # Build for production
pnpm inspect      # Open MCP Inspector at localhost:6274

Architecture

                                                   +--> PriceService ──> OracleProvider(s)
                                                   |
stdio transport ──> McpServer ──> 16 tools ──> HorizonClient ──> Stellar Horizon REST API
                                                   |
HTTP transport  ──> Express ──> x402 middleware ────+
                       |
                       +-- /tools/* (paid endpoints)
                       +-- /tools/getNetworkStatus (free)
                       +-- /health (free)
                       +-- /pricing (free)
                       +-- /skill.md (OpenClaw discovery)

The PriceService sits on top of HorizonClient and provides normalized price data (current price, OHLC history, VWAP) through an oracle abstraction layer. The SDEX oracle queries Horizon trade aggregations; future oracles (Reflector, Chainlink) plug in via the same OracleProvider interface.

Tech Stack

• TypeScript with strict mode
• Node.js 22+
• MCP SDK (@modelcontextprotocol/sdk)
• x402 (@x402/express, @x402/stellar, @x402/core)
• Express 4 with CORS and rate limiting
• Vitest for testing
• tsup for bundling

Environment Variables

See .env.example for all options.

Variable	Required	Default	Description
STELLAR_NETWORK	No	testnet	testnet or pubnet
HORIZON_URL	No	https://horizon-testnet.stellar.org	Horizon API URL
TRANSPORT	No	stdio	stdio or http
STELLAR_PAYEE_ADDRESS	HTTP mode	—	Your Stellar address for receiving payments
OZ_FACILITATOR_URL	HTTP mode	—	OpenZeppelin x402 facilitator URL
OZ_API_KEY	HTTP mode	—	OpenZeppelin facilitator API key
PORT	No	4021	HTTP server port
LOG_LEVEL	No	info	debug, info, warn, error
SOROBAN_RPC_URL	No	—	Soroban RPC URL (for future SEP-41 token support)

License

MIT