mcp-agent-app

mcp-agent-app

A TypeScript service that converts GeoJSON geometries into 3D triangulated meshes using a local LLM (Ollama). It exposes an MCP tool (generate_mesh) and an HTTP API, making mesh generation accessible both to MCP-compatible clients and standard REST consumers.

POST /generate-mesh
        │
        ▼
  Express API (src/api/index.ts)
        │
        ▼
  generateMeshAgent (src/agents/generate_mesh_agent.ts)
        │
        ▼
  Ollama LLM  ──────────────────────────────────────────>  MeshData
  (llama3.2 @ localhost:11434)                             { vertices, indices, metadata }

MCP server (src/server.ts) exposes the same agent as an MCP tool over stdio

Stack

| Layer | Technology | |---|---| | Language | TypeScript 5 (strict, ES2022, ESM) | | Runtime | Node.js 18+ with tsx for development | | Web framework | Express 4 | | MCP SDK | @modelcontextprotocol/sdk v1.29, @modelcontextprotocol/server v2.0 alpha | | Schema validation | Zod | | Local LLM | Ollama (llama3.2 at http://localhost:11434) |

Note: The MCP server and HTTP API use Ollama for inference — no Anthropic API key is required for the core mesh generation. ANTHROPIC_API_KEY is only needed if you extend the agent loop with Claude tool-use.

Project structure

src/
├── server.ts                     # MCP server — registers and runs the generate_mesh tool
├── agents/
│   └── generate_mesh_agent.ts    # Core logic: GeoJSON → Ollama → MeshData
└── api/
    └── index.ts                  # Express HTTP API wrapping the agent

Prerequisites

1. Node.js 18+
2. Ollama running locally with the llama3.2 model pulled:

   ollama pull llama3.2
   ollama serve          # must be running on http://localhost:11434

Setup

npm install

Run (dev, no build step)

npm run dev    # starts the Express API on port 3000 (default)

In another terminal:

curl -X POST http://localhost:3000/generate-mesh \
  -H "Content-Type: application/json" \
  -d '{"geometry": "{\"type\":\"Polygon\",\"coordinates\":[[[0,0],[1,0],[1,1],[0,1],[0,0]]]}"}'

The geometry field accepts either a JSON string or a parsed GeoJSON object (Geometry or Feature).

Expected response shape:

{
  "vertices": [0, 0, 0, 1, 0, 0, ...],
  "indices":  [0, 1, 2, ...],
  "metadata": {
    "featureType": "Polygon",
    "vertexCount": 8,
    "triangleCount": 4
  }
}

Mesh conventions

| Geometry type | Mesh output | |---|---| | Polygon / MultiPolygon | Flat base (z=0) + extruded top (z=10) + side walls | | LineString | Ribbon mesh, width 0.0001° | | Point | Small pyramid |

Coordinates map as: longitude → x, latitude → y, elevation → z.

Build & run (production)

npm run build
npm start

Run the MCP server standalone

npm run mcp
# or inspect it interactively:
npx @modelcontextprotocol/inspector npx tsx src/server.ts

The MCP server exposes one tool — generate_mesh — that accepts a GeoJSON geometry or Feature as a JSON string and returns the same MeshData structure as the HTTP API.

NPM scripts

| Script | Description | |---|---| | npm run dev | Start API in watch mode via tsx | | npm start | Run compiled dist/api/index.js | | npm run build | Compile TypeScript to dist/ | | npm run mcp | Run the MCP server standalone |

Environment variables

| Variable | Default | Description | |---|---|---| | PORT | 3000 | Express server port | | CORS_ORIGINS | http://localhost:5173 | Comma-separated list of allowed CORS origins |

Notes

• The MCP server logs to stderr, never stdout — stdout is the stdio protocol channel.
• Ollama responses are validated with a Zod schema; a regex fallback handles markdown-wrapped JSON output.
• The HTTP API allows requests with no Origin header (server-to-server calls) in addition to the CORS allowlist.
• For production: TLS at a reverse proxy, auth + rate limiting in front of /generate-mesh, and request timeouts via AbortController.
• To swap in a remote MCP server, replace StdioClientTransport with StreamableHTTPClientTransport in the MCP manager.