ChemCP

What it does

ChemCP renders interactive 2D molecular structure diagrams from SMILES notation directly inside Claude's chat interface. Ask for any molecule — aspirin, caffeine, testosterone — and get a visual structure diagram with computed molecular properties displayed in a sandboxed iframe. Built on RDKit.js (WebAssembly), it brings pharma-grade cheminformatics to your AI assistant.

Key features

• 2D structure rendering — any valid SMILES string becomes a clean SVG molecular diagram
• Computed molecular properties — molecular weight, LogP, H-bond donors/acceptors, TPSA, rotatable bonds, ring count, and more
• Interactive UI — type your own SMILES, click example molecules, all within the conversation
• RDKit.js powered — the same cheminformatics toolkit used in pharmaceutical research, running client-side via WebAssembly
• Dual transport — supports both stdio (Claude Desktop) and HTTP (Claude.ai with tunnel)

Installation

Claude Desktop (recommended)

{
  "mcpServers": {
    "chemcp": {
      "command": "npx",
      "args": ["chemcp"]
    }
  }
}

Add to claude_desktop_config.json, then restart Claude Desktop.

Claude.ai (web — experimental)

Install and run in HTTP mode:

npm install -g chemcp
chemcp --http

Expose with a tunnel (e.g. npx cloudflared tunnel --url http://localhost:3001) and add the tunnel URL + /mcp as a custom connector in Settings → Connectors.

VS Code Copilot

Not confirmed in README.

Supported hosts

• Claude Desktop — full MCP Apps support, recommended
• Claude.ai — experimental, may have CSP limitations preventing RDKit.js from loading