mcp-server-cantrip

mcp-server-cantrip

MCP (Model Context Protocol) server for Cantrip — the AI-powered GTM engine for solo founders.

This server lets any MCP-compatible agent (Claude, Cursor, etc.) interact with Cantrip's project management, gap analysis, and entity CRUD through the standard MCP tool protocol.

Architecture

Agent (Claude, etc.) ── MCP protocol (stdio) ──> mcp-server-cantrip ── HTTPS POST ──> https://api.cantrip.ai

The MCP server is a thin translation layer. It converts MCP tool calls into {command, args, flags} JSON envelopes and POSTs them to the Cantrip API. Zero business logic — identical contract to the CLI and React UI.

Installation

npm install -g mcp-server-cantrip

Or run directly (used by the configs below):

npx -y mcp-server-cantrip

Getting Your API Key

• Sign up at cantrip.ai
• Get your API key at dashboard.cantrip.ai/settings/api-keys

Configuration

Claude Code (recommended: CLI one-liner)

claude mcp add cantrip -e CANTRIP_API_KEY=your-api-key -- npx -y mcp-server-cantrip

This registers the server in ~/.claude.json with local scope. Verify with:

claude mcp list

Or check status inside Claude Code with the /mcp command.

Claude Code (manual JSON)

If you prefer editing config directly, add to ~/.claude.json:

{
  "mcpServers": {
    "cantrip": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "mcp-server-cantrip"],
      "env": {
        "CANTRIP_API_KEY": "your-api-key"
      }
    }
  }
}

Important: The -y flag is required. Without it, npx prompts for install confirmation which hangs because stdio is consumed by the MCP protocol.

Claude Code (project-scoped, shared with team)

Add a .mcp.json file to your project root:

{
  "mcpServers": {
    "cantrip": {
      "command": "npx",
      "args": ["-y", "mcp-server-cantrip"],
      "env": {
        "CANTRIP_API_KEY": "${CANTRIP_API_KEY}"
      }
    }
  }
}

This uses environment variable expansion so API keys stay out of version control. Each developer sets CANTRIP_API_KEY in their shell profile.

Claude Desktop

macOS: Edit ~/Library/Application Support/Claude/claude_desktop_config.json

Windows: Edit %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "cantrip": {
      "command": "npx",
      "args": ["-y", "mcp-server-cantrip"],
      "env": {
        "CANTRIP_API_KEY": "your-api-key"
      }
    }
  }
}

Cursor

Add to .cursor/mcp.json in your project or ~/.cursor/mcp.json globally:

{
  "mcpServers": {
    "cantrip": {
      "command": "npx",
      "args": ["-y", "mcp-server-cantrip"],
      "env": {
        "CANTRIP_API_KEY": "your-api-key"
      }
    }
  }
}

Windows Note

On native Windows (not WSL), wrap the command with cmd /c:

{
  "mcpServers": {
    "cantrip": {
      "command": "cmd",
      "args": ["/c", "npx", "-y", "mcp-server-cantrip"],
      "env": {
        "CANTRIP_API_KEY": "your-api-key"
      }
    }
  }
}

Project Context (.cantrip.json)

Each project directory contains a .cantrip.json file that tells Cantrip which project to target:

{
  "project": "my-saas"
}

This file is created automatically by cantrip_init (new project) or cantrip_connect (existing project). The agent manages it — you don't need to create it manually.

Multiple projects on the same machine? Each project directory gets its own .cantrip.json. The agent switches context by working in the right directory.

Troubleshooting

Server not found / no tools appear:

• Run claude mcp list (Claude Code) or /mcp inside a session to check connection status.
• Make sure the config is in the right file — Claude Code uses ~/.claude.json or .mcp.json, not ~/.claude/mcp.json.

Server hangs on startup:

• Ensure you have -y in the npx args. Without it, npx waits for interactive confirmation that can never arrive over stdio.

"Cannot reach Cantrip API" errors:

• Verify CANTRIP_API_KEY is set in the env block of your MCP config.
• Check that https://api.cantrip.ai is reachable from your network.

Windows "Connection closed" errors:

• Use "command": "cmd" with "args": ["/c", "npx", "-y", "mcp-server-cantrip"].

Tools (17)

Setup

Tool	Description
cantrip_connect	Connect workspace to a project (reads/writes .cantrip.json)
cantrip_status	Check if the daemon is running
cantrip_init	Create a new project and auto-connect

Core Commands

Tool	Description
cantrip_snapshot	Project overview, drill into entity types
cantrip_next	List gap-analysis opportunities
cantrip_next_prompt	Generate a context-rich LLM prompt for an opportunity
cantrip_next_run	Spawn a background agent for an opportunity
cantrip_history	Query the audit trail

Review

Tool	Description
cantrip_review	List items pending review
cantrip_review_accept	Accept an inferred entity
cantrip_review_reject	Reject an inferred entity
cantrip_review_resolve	Resolve an escalation
cantrip_review_dismiss	Dismiss an escalation

Entity CRUD (generic)

Tool	Description
cantrip_entity_list	List entities of a type
cantrip_entity_show	Show entity detail
cantrip_entity_add	Create a new entity
cantrip_entity_edit	Edit an existing entity

Supported entity types: icp, pain_point, value_prop, experiment, channel, competitor, contact

License

MIT