Build with WebMCP in the OpenAI WebMCP Challenge
Build an agent-native web app, test it in ChatGPT, and submit it by September 3.
The OpenAI WebMCP Challenge is open. From August 25 through September 3, builders can create a new agent-native web app or add WebMCP to an existing one, then use it with ChatGPT's in-app browser.
WebMCP is an experimental open web proposal that lets a site publish structured tools for an agent. The site defines the actions, inputs, and descriptions. The person and the agent stay in the same live app, so the work remains visible and sensitive actions can still ask for confirmation.
Submission window
Submissions close September 3 at 1 p.m. PT. Check the official competition page for current rules, eligibility, prizes, and deadlines.
What to build
Start with one workflow your app already understands. A good WebMCP tool should let an agent complete a meaningful task with fewer steps while keeping the result easy for a person to inspect and change.
- Pick a real task. Search, compare, create, update, or submit something your app already owns.
- Expose the smallest useful tool surface. Give each tool a clear name, description, and input schema instead of mirroring every button on the page.
- Test the human-agent handoff. Let the agent do the mechanical work, then keep review, edits, and sensitive confirmations visible in the product UI.
The judging rubric looks at WebMCP leverage, execution, potential impact, and creativity and ambition. A focused workflow that feels finished will beat a wide tool surface with no clear user benefit.
Use MCP-B or the browser API directly
You can build directly against the proposed document.modelContext API. MCP-B
adds open-source packages for typed tool registration, React integrations, polyfills,
transports, and browser tooling when your app needs them.
- New to the project? Choose a path through the docs.
- Adding tools to a live product? Follow Add tools to an existing app.
- Unsure which package layer fits? Choose a runtime.
Key dates
- Kickoff livestream
- Community office hours
- Submissions close
- Winners announced
Build something only WebMCP makes practical
Focus on what people can do when an agent understands the app's real actions and works through the same interface they use. Pick that moment, make it reliable, and submit it.