WebMCP Challenge demo

CarCare MCP

A tiny vehicle maintenance app where humans see a simple dashboard and AI agents get explicit WebMCP tools to read records, add service, and calculate what comes next.

My Vehicle

2011 Toyota Sienna

3.5L V6

165,200 miles

Maintenance History

  • Engine Oil 163,000 miles · 2026-08-01 Oil and filter change.
    ✓
  • Transmission Fluid 160,000 miles · 2026-07-20 Drain and fill automatic transmission fluid.
    ✓
  • Air Filter 155,000 miles · 2026-05-12 Cabin and engine air filter inspected; engine filter replaced.
    ✓
  • Brake Pads 150,000 miles · 2026-03-18 Front pads replaced.
    ✓

Storage model

Private, backend-free demo data

CarCare stores demo records in this browser's localStorage. Records persist after refresh and browser restart, but they do not sync across devices, browsers, or Chrome profiles. Use Reset demo data any time to restore the seeded Toyota Sienna history.

Copy-paste agent prompt

Try a full WebMCP workflow

Open this page in a WebMCP-capable browser, then ask your agent:

Look up my vehicle, review the maintenance history, then add one combined visit record: I changed the engine oil at 2026-09-05 at 175,500 miles using 0W-20 full synthetic oil and Tire Rotation. Add this to my maintenance history, keep same-date same-mileage services together, and tell me when the next oil change and tire rotation are due.

Add Maintenance

Agent tools exposed by WebMCP

Instead of guessing which button to click, an agent can call explicit tools registered with document.modelContext.registerTool:

  • get_vehicle()
  • get_maintenance_history()
  • add_maintenance_record(service, mileage, date, notes)
  • edit_maintenance_record(id, service, mileage, date, notes)
  • calculate_next_service(service)
  • search_maintenance_records(query)

WebMCP self-test

Checking whether this browser exposes document.modelContext...