Breakpoint Engine

Use Breakpoint Engine in ChatGPT

Breakpoint Engine connects to ChatGPT as a custom MCP app. Once connected, ChatGPT can call the opm_* tools directly in your chat — estimate work, run OPM forwardsolves and backsolves, explain breakpoints, and step through interactive scenarios on a cap table you paste into the conversation.

Looking for Breakpoint Engine in the ChatGPT Plugins Directory? It is not listed there yet. Until it is, you add it as a custom MCP app by URL using the steps below — same tools, no directory listing required. All opm_* tools are pure computation: they read the cap table you provide and return numbers. Nothing is stored and nothing outside the conversation is changed.

Requirements

  • ChatGPT Business, Enterprise, or Edu — full custom MCP app support (beta), managed by workspace admins. ChatGPT Pro — individuals can connect MCP apps with read-level tools in developer mode.
  • ChatGPT on the web — custom MCP apps are not available on mobile.
  • A Breakpoint Engine account with work-unit credits — create an account and buy a Round, Portfolio, or Practice pack.

Setup — personal account (Pro)

  1. Sign in at breakpointengine.com/account and purchase a credit pack (the connector meters work units against your balance).
  2. In ChatGPT, open Settings → Apps → Advanced settings and enable Developer mode.
  3. Go to Settings → Apps → Create and enter:
    • Name: Breakpoint Engine
    • MCP server URL: https://cloud.breakpointengine.com/mcp
    • Authentication: OAuth. Leave client ID and secret blank — the server supports dynamic client registration, so ChatGPT registers itself.
  4. Click Scan Tools, complete the Auth0 sign-in when prompted (same account you purchased credits with), and wait for the scan to finish. Then click Create.
  5. The app appears under Settings → Apps → Enabled Apps with a Dev label. In a new chat, select it from the tools menu (or mention it by name) and ask ChatGPT to call opm_schema to confirm the connection.

Setup — Business / Enterprise / Edu workspace

  1. An admin or owner enables Developer mode — Business: User Settings → Apps → Advanced settings (each admin toggles it for themselves); Enterprise/Edu: grant access under Permissions & Roles → Connected Data, then enabled members toggle Settings → Apps → Advanced Settings.
  2. Create the app from Workspace settings → Apps → Create with the same name, URL, and OAuth settings as above; run Scan Tools and complete the Auth0 prompt.
  3. The app lands in Workspace Settings → Apps → Drafts. Test it in a chat, then an admin clicks Publish to make it available to the workspace. Enterprise/Edu admins can scope access and allowed actions with RBAC before publishing.
  4. Note: on Business plans a published app cannot be edited — to change tools or metadata, recreate and republish. Tool definitions are frozen at approval; if the server's tools change later, an admin refreshes them from Workspace settings.

First valuation in chat

  1. Paste your cap table and assumptions in the documented JSON format — or describe your share classes in plain language and ask ChatGPT to build the JSON, then confirm it.
  2. Ask for an estimate first: "Call opm_estimate for this cap table."
  3. Then run: "Run opm_forwardsolve with max_work set from the estimate." For a backsolve from a recent round price, use opm_backsolve.

ChatGPT may show an approval card before tool calls depending on your app permission setting (the default is Important actions). Deep research can use the connector for read/fetch only; agent mode does not use custom apps.

Troubleshooting

  • No Create option under Apps — Developer mode must be on (Settings → Apps → Advanced settings), and on workspace plans only admins/authorized members can create apps.
  • OAuth / registration error — leave client ID and secret blank so ChatGPT can register dynamically; confirm you can sign in at /account with the same identity.
  • Connection failed / 401 — re-authorize the connector; the OAuth token may have expired (tokens last about one hour and refresh on reconnect).
  • insufficient_credits (402) — your work-unit balance is empty; buy another pack on account.
  • App missing in chat — Developer mode must remain enabled, and the app must be selected in the chat's tools menu.

Cap tables are never stored — computation, not custody. Also see Claude setup, Cursor setup, and the tool reference.