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

• 17 MCP tools querying Stellar Horizon REST + Soroban contracts (SEP-41 tokens)

• Multi-oracle price aggregation with median computation and source attribution across SDEX and Reflector

• PriceService with VWAP, OHLC history, and oracle abstraction layer

• x402 micropayments on Stellar — agents pay per call in USDC

• Triple transport — stdio for local MCP clients, HTTP REST for x402-gated access, MCP-over-HTTP at /mcp (StreamableHTTPServerTransport with stateful sessions) for remote MCP clients

• 132 tests — 106 unit + 26 live testnet integration

• Production-ready — multi-stage Dockerfile, mainnet auto-defaults, enriched /health, self-service /docs page with embedded Swagger UI

• Earn/spend demo + trading strategies — SMA crossover, cross-pair arbitrage, real x402 settlement loop

• OpenClaw compatible — permissionless agent discovery via GET /skill.md

• Zero @stellar/stellar-sdk in production bundle — raw fetch to Horizon, dynamic import only for Soroban contract simulation

Related MCP server: opendexter

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"
      }
    }
  }
}

MCP Client (HTTP — remote)

Connect to a running StellarMCP HTTP server from any MCP client that supports the StreamableHTTP transport. Point your client at http://<host>:4021/mcp — the same McpServer instance with all 17 tools is shared between the stdio and HTTP transports.

# Start the HTTP server (also serves /mcp)
TRANSPORT=http pnpm start

# MCP clients connect via POST/GET/DELETE http://localhost:4021/mcp
# Stateful sessions are tracked via the mcp-session-id header.

The /mcp endpoint is free (not x402-gated). Per-tool x402 gating applies to the REST endpoints under /tools/*.

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

# Connect an MCP client via MCP-over-HTTP
# POST http://localhost:4021/mcp  (JSON-RPC)
# GET  http://localhost:4021/mcp  (SSE stream)

Tools

Horizon Data Tools

Price Tools

The price tools are powered by PriceService, which aggregates data from the Stellar SDEX via trade aggregations. A PriceAggregator layer combines multiple oracle sources (currently SdexOracle + ReflectorOracle stub) and returns a median price along with a sources[] array containing {name, price, timestamp} entries for full attribution. Additional oracles (Chainlink, Redstone, Band) plug into the same OracleProvider interface.

Soroban Token Tools

Requires SOROBAN_RPC_URL to be configured. Uses Soroban contract simulation (read-only, no fees).

Asset Format

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:

1. Earns USDC by receiving x402 payments from clients querying Stellar data

2. 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

stdio transport ──> McpServer ──> 17 tools ──> HorizonClient ──> Stellar Horizon REST API
                        │                          │
                        │                          ├── PriceService
HTTP transport  ──> Express ──┬── /tools/* (REST + x402)
                              ├── /mcp (StreamableHTTPServerTransport)
                              └── /pricing, /health, /skill.md (free)
                        │
                        └── PriceAggregator → [SdexOracle, ReflectorOracle]

Both the stdio and HTTP transports share the same McpServer instance with all 17 tools registered. The /mcp endpoint is a MCP-over-HTTP bridge (POST/GET/DELETE) using StreamableHTTPServerTransport with stateful sessions tracked via the mcp-session-id header — giving remote MCP clients the full protocol (tools, resources, prompts) without stdio.

The PriceService sits on top of HorizonClient and provides normalized price data (current price, OHLC history, VWAP). The PriceAggregator layer fans out queries to multiple OracleProviders (SdexOracle + ReflectorOracle today) and computes a median with per-source attribution. Additional oracles (Chainlink, Redstone) plug in via the same 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.

Documentation

• Architecture — component map, data flow, key design decisions (8 Mermaid diagrams)

• Metrics — verifiable current state evidence (every metric reproducible from this repo)

• Deployment — production deployment guide (Docker, PM2, systemd, nginx, Caddy, monitoring, security)

• MCP Registry submission — guide for publishing to the official MCP Registry

• x402 Bazaar registration — guide for registering on the Coinbase CDP x402 Bazaar

• OpenAPI spec — full OpenAPI 3.1 spec for all 22 endpoints

• Live /docs page — when the HTTP server is running, visit http://localhost:4021/docs for an embedded Swagger UI

License

MIT