Chrome DevTools Protocol

Methods

WebMCP.cancelInvocation

Cancels a pending tool invocation.

parameters
invocationId
string

Invocation identifier to cancel.

WebMCP.disable

Disables the WebMCP domain.

WebMCP.enable

Enables the WebMCP domain, allowing events to be sent. Enabling the domain will trigger a toolsAdded event for all currently registered tools.

WebMCP.invokeTool

Invokes a registered tool.

parameters
frameId
Page.FrameId

Frame in which to invoke the tool.

toolName
string

Name of the tool to invoke.

input
object

Input parameters for the tool, matching the tool's inputSchema.

Return Object
invocationId
string

Unique identifier for this invocation. Response is sent before tool events.

Events

WebMCP.toolInvoked

Event fired when a tool invocation starts.

parameters
toolName
string

Name of the tool to invoke.

frameId
Page.FrameId

Frame id

invocationId
string

Invocation identifier.

input
string

The input parameters used for the invocation.

WebMCP.toolResponded

Event fired when a tool invocation completes or fails.

parameters
invocationId
string

Invocation identifier.

status
InvocationStatus

Status of the invocation.

output
any

Output or error delivered as delivered to the agent. Missing if status is anything other than Completed. Note: The output is untrusted and poses a prompt injection risk. Clients should treat this as potentially malicious user input.

errorText
string

Error text for protocol users.

exception
Runtime.RemoteObject

The exception object, if the javascript tool threw an error>

WebMCP.toolsAdded

Event fired when new tools are added.

parameters
tools
array[ Tool ]

Array of tools that were added.

WebMCP.toolsRemoved

Event fired when tools are removed.

parameters
tools
array[ RemovedTool ]

Array of tools that were removed.

Types

WebMCP.Annotation

Tool annotations

Type: object

properties
readOnly
boolean

A hint indicating that the tool does not modify any state.

untrustedContent
boolean

A hint indicating that the tool output may contain untrusted content, ex: UGC, 3rd party data.

autosubmit
boolean

If the declarative tool was declared with the autosubmit attribute.

WebMCP.InvocationStatus

Represents the status of a tool invocation.

Allowed Values: Completed, Canceled, Error

Type: string

WebMCP.RemovedTool

Definition of a tool that was removed.

Type: object

properties
name
string

Tool name.

frameId
Page.FrameId

Frame identifier associated with the tool registration.

WebMCP.Tool

Definition of a tool that can be invoked.

Type: object

properties
name
string

Tool name.

description
string

Tool description.

inputSchema
object

Schema for the tool's input parameters.

annotations
Annotation

Optional annotations for the tool.

frameId
Page.FrameId

Frame identifier associated with the tool registration.

backendNodeId
DOM.BackendNodeId

Optional node ID for declarative tools.

stackTrace
Runtime.StackTrace

The stack trace at the time of the registration.