WebMCP integration reference

ViewCue integrates with the page-side WebMCP surface exposed as document.modelContext.

Host-owned tools

The host application registers domain tools:

await document.modelContext.registerTool({
  name: "prepare_payment",
  title: "Prepare a payment method",
  description: "Prepare a synthetic payment method preview.",
  inputSchema: {
    type: "object",
    properties: {
      method: { type: "string", enum: ["qris", "bank_transfer", "deposit"] },
    },
    required: ["method"],
    additionalProperties: false,
  },
  execute: async ({ method }) => {
    // Host application owns this behavior.
    choosePaymentMethod(method)
    return JSON.stringify({ ok: true, method, simulation: true })
  },
})

ViewCue helper tools

When WebMCP is supported, the standalone bundle can register:

Tool	Purpose
get_visible_ui_context	Read bounded visible targets and current clue context
show_ui_clue	Show a clue at a registered target
clear_ui_guidance	Remove the current clue

These are presentation helpers. They do not replace the host application’s domain tools.

Registration behavior

The integration feature-detects document.modelContext.registerTool(). If WebMCP is unavailable, the visual runtime still works for host UI calls.

The current experimental WebMCP API is page-scoped. The agent must be connected to the open page to discover and invoke its tools.