Use Breakpoint Engine in Cursor and VS Code

Two ways to connect: the hosted cloud MCP endpoint (metered, OAuth), or a private local Docker build of the open-source engine (unmetered — cap tables never leave your machine).

Before you connect (cloud)

1. Create an account (Auth0).
2. Buy a Round, Portfolio, or Practice pack and confirm balance on Account.
3. Use the same identity for the OAuth prompt in Cursor or VS Code.

Cursor — cloud (Streamable HTTP)

1. Add to your project's .cursor/mcp.json (or global ~/.cursor/mcp.json, or Cursor Settings → MCP):

   {
     "mcpServers": {
       "breakpointengine-cloud": {
         "url": "https://cloud.breakpointengine.com/mcp"
       }
     }
   }

2. Reload MCP servers (or reopen the folder).
3. When the server shows Needs authentication (or only exposes mcp_auth), click Connect and complete Auth0 in the browser.
4. Confirm tools appear, then ask your agent to call opm_schema. No client ID or secret is required — Cursor registers itself with Auth0 via dynamic client registration.

Cursor desktop uses the loopback callback http://localhost:8787/callback (some builds also use a cursor:// deeplink). You do not configure redirect URIs in mcp.json.

Cursor — local (Docker stdio)

1. Clone and build the open-source engine:

   git clone https://github.com/breakpointengine/breakpointengine.git
   cd breakpointengine
   docker compose build opm-mcp

2. Add to .cursor/mcp.json:

   {
     "mcpServers": {
       "breakpointengine": {
         "command": "docker",
         "args": ["run", "-i", "--rm", "breakpointengine/opm-mcp:local"]
       }
     }
   }

3. Reload, then ask your agent to call opm_schema and read opm://schema/cap_table.

VS Code (Copilot MCP) — cloud

Requires VS Code 1.101+ with Copilot Chat Agent mode.

1. Add to .vscode/mcp.json (note the servers key):

   {
     "servers": {
       "breakpointengine-cloud": {
         "type": "http",
         "url": "https://cloud.breakpointengine.com/mcp"
       }
     }
   }

2. Or run MCP: Add Server → HTTP → paste https://cloud.breakpointengine.com/mcp.
3. Start the server; complete Auth0 when the browser opens. Leave any optional OAuth client ID empty.
4. In Copilot Chat (Agent), ask for opm_schema.

VS Code — local

{
  "servers": {
    "breakpointengine": {
      "type": "stdio",
      "command": "docker",
      "args": ["run", "-i", "--rm", "breakpointengine/opm-mcp:local"]
    }
  }
}

Working pattern

1. Prepare inputs in the cap table JSON format.
2. opm_estimate → set max_work → opm_forwardsolve / opm_backsolve.
3. For interactive round design: opm_scenario_begin → step / query / mutate / branch / diff → commit.

Troubleshooting

• Stuck on Needs authentication — finish Connect / mcp_auth; check Output → MCP Logs.
• OAuth or registration error — confirm you can sign in at /account; the cloud tenant must allow dynamic client registration (operator-side Auth0 setting).
• Tools load then every call is 401 — reconnect; the access token must be a JWT for the cloud API audience.
• 402 / insufficient_credits — buy another pack on account or lower max_work.

Also see ChatGPT setup, Claude setup, and the tool reference.