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Imperative WebMCP API Reference

Option	Type	Description
registerTool(tool, options) — `tool` properties
`name`	String	Unique identifier for the tool. Letters, digits, hyphens, underscores, and dots. Max 128 characters.
`description`	String	Human-readable description of what the tool does. Helps the agent decide when and how to use it.
`title`	String	Optional. Friendly display name shown in UIs (the agent uses `name` for invocation).
`inputSchema`	Object	JSON Schema describing the input parameters the tool accepts. See json-schema.org.
`annotations`	Object	Optional hints for the agent. `readOnlyHint: true` means the tool doesn’t mutate state. `untrustedContentHint: true` means the tool’s output may contain untrusted content. `consequentialHint: true` indicates an action with significant consequences, such as making a payment. Omitted hints default to `false` when an annotations object is supplied.
`execute`	Function	Called when the agent invokes the tool. Receives an object matching `inputSchema` and an options object whose `signal` is aborted if the invocation is canceled. Can be sync or async. Return value is sent back to the agent.
registerTool(tool, options) — `options` properties
`signal`	AbortSignal	Optional. Pass an `AbortController.signal` to later unregister the tool by calling `controller.abort()`.
`exposedTo`	Array<String>	Optional. Origins (e.g. `"https://example.com"`) that an iframe wants to share this tool with. Use to bubble a tool up from a cross-origin iframe to its parent document.
Discovering tools — `document.modelContext.getTools(options?)`
`fromOrigins`	Array<String>	Optional. Include tools from the listed origins if they are exposed to the calling document, in addition to same-origin tools. An omitted or empty list returns only same-origin tools. Returns a `Promise<RegisteredTool[]>`.
Unregistering tools
`AbortController`	Object	Create a controller, pass `controller.signal` to `registerTool()`. Call `controller.abort()` to unregister the tool at any time.