Your site just got a second user.
WebMCP gives agents real tools on your pages — the same actions your buttons perform, as callable functions. This page's registry is live.
document.modelContext.registerTool(…) — live on this page
Correctness testing for WebMCP appsYour app will approve
Your app will approve
what nobody reviewed.
Paradox is a testing tool for WebMCP apps — it finds these races and proves the fix against every explored future.
bun add github:Joe-Simo/paradox-webmcpThe race
The agent inspects $2,399 · v7. Agent inspected 2,399 dollars at version 7 and created a version 7 review.
The race is real.
Every operator followed the rules. The system still broke its own.
inspect_expenseapprove_reviewed_expense
Every ordering, explored.
Paradox tries every ordering of the recorded actions and checks each outcome against one rule: approved = reviewed.
explore_futures
The guard goes in.
The shortest failure is isolated, and a version guard goes into the approval tool.
inspect_counterexampleapply_version_guard
The color leaves the universe.
The same failing sequence replays as blocked. Nothing survives re-exploration.
verify_repair