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.