WebMCP

page.tools() returns page-bound WebMCPTool objects. Invoking a tool returns a WebMCPInvocation, which can wait for Chrome’s terminal response or request cancellation. See the Page reference for tool discovery options.

TypeScript
Python
Go

WebMCPTool

Properties

Property	Type	Description
`name`	`string`	Tool name used for invocation.
`description`	`string`	Human-readable tool description.
`inputSchema`	`Record<string, unknown> \| undefined`	Optional JSON input schema.
`annotations`	`WebMCPAnnotation \| undefined`	Optional `readOnly`, `untrustedContent`, and `autosubmit` flags.
`frameId`	`string`	Frame that published the tool.
`backendNodeId`	`number \| undefined`	Optional non-negative backend node identifier.

invoke()

invoke(options?: WebMCPInvokeOptions): Promise<WebMCPInvocation>

options.input is a JSON-compatible object and defaults to {}. The helper supplies its own page, frame, and tool name.

WebMCPInvocation

Properties

Property	Type	Description
`invocationId`	`string`	Stable invocation identifier.
`toolName`	`string`	Name of the invoked tool.
`frameId`	`string`	Frame handling the invocation.
`input`	`Record<string, unknown>`	JSON input sent to the tool.

result()

result(options?: WebMCPResultOptions): Promise<WebMCPToolResponse>

options.timeout is an optional non-negative timeout in milliseconds. A successful terminal response is cached on the invocation; timeout and transport failures are not cached and can be retried.

Response field	Type	Description
`invocationId`	`string`	Invocation that produced the response.
`status`	`"Completed" \| "Canceled" \| "Error"`	Terminal status.
`output`	`unknown`	Optional JSON output.
`errorText`	`string \| undefined`	Optional error message.
`exception`	`WebMCPRemoteObject \| undefined`	Optional structured exception data.

cancel()

cancel(): Promise<void>

Requests cancellation from Chrome. It does not synthesize or overwrite a terminal response; call result() for the authoritative final status.

WebMCPTool

Properties

Property	Type	Description
`name`	`str`	Tool name used for invocation.
`description`	`str`	Human-readable tool description.
`input_schema`	`dict[str, JsonValue] \| None`	Optional JSON input schema.
`annotations`	`WebMCPAnnotation \| None`	Optional `read_only`, `untrusted_content`, and `autosubmit` flags.
`frame_id`	`str`	Frame that published the tool.
`backend_node_id`	`int \| None`	Optional non-negative backend node identifier.

invoke()

async def invoke(
    *,
    input: Mapping[str, JsonValue] | None = None,
) -> WebMCPInvocation

input defaults to an empty dictionary. The helper supplies its own page, frame, and tool name.

WebMCPInvocation

Properties

Property	Type	Description
`invocation_id`	`str`	Stable invocation identifier.
`tool_name`	`str`	Name of the invoked tool.
`frame_id`	`str`	Frame handling the invocation.
`input`	`dict[str, JsonValue]`	JSON input sent to the tool.

result()

async def result(*, timeout: float | None = None) -> WebMCPToolResponse

timeout is an optional non-negative timeout in milliseconds. A successful terminal response is cached; timeout and transport failures are not cached and can be retried.

Response field	Type	Description
`invocation_id`	`str`	Invocation that produced the response.
`status`	`Literal["Completed", "Canceled", "Error"]`	Terminal status.
`output`	`JsonValue \| None`	Optional JSON output.
`error_text`	`str \| None`	Optional error message.
`exception`	`dict[str, JsonValue] \| None`	Optional structured exception data.

cancel()

async def cancel() -> None

Requests cancellation from Chrome. It does not synthesize or overwrite a terminal response; call result() for the authoritative final status.

WebMCPTool

Go exposes descriptor data through a method rather than properties.

Descriptor()

func (t *WebMCPTool) Descriptor() WebMCPToolDescriptor

The returned descriptor contains Name, Description, InputSchema, Annotations, FrameID, and optional BackendNodeID. Annotations may contain ReadOnly, UntrustedContent, and Autosubmit pointers.

Invoke()

func (t *WebMCPTool) Invoke(
    ctx context.Context,
    input WebMCPInput,
) (*WebMCPInvocation, error)

WebMCPInput is a map[string]any; nil is sent as an empty JSON object. Values must be JSON encodable. The helper supplies its own page, frame, and tool name.

WebMCPInvocation

Descriptor()

func (i *WebMCPInvocation) Descriptor() WebMCPInvocationDescriptor

The descriptor contains InvocationID, ToolName, FrameID, and the JSON Input map.

Result()

func (i *WebMCPInvocation) Result(
    ctx context.Context,
    options *WebMCPResultOptions,
) (WebMCPToolResponse, error)

Pass nil for default waiting behavior. options.Timeout is an optional non-negative timeout in milliseconds. A successful terminal response is cached; context and RPC failures are not cached and can be retried.

Response field	Type	Description
`InvocationID`	`string`	Invocation that produced the response.
`Status`	`WebMCPInvocationStatus`	`WebMCPInvocationStatusCompleted`, `WebMCPInvocationStatusCanceled`, or `WebMCPInvocationStatusError`.
`Output`	`json.RawMessage`	Optional JSON output.
`ErrorText`	`*string`	Optional error message.
`Exception`	`WebMCPRemoteObject`	Optional structured exception data.

Use WebMCPOutputAs[T](response) to decode a non-empty JSON output into a caller-selected type.

Cancel()

func (i *WebMCPInvocation) Cancel(ctx context.Context) error

Requests cancellation from Chrome. It does not synthesize or overwrite a terminal response; call Result() for the authoritative final status.

First steps

The basics

Configuration

Best practices

Migration guide

SDK reference

WebMCPTool

Properties

invoke()

WebMCPInvocation

Properties

result()

cancel()

WebMCPTool

Properties

invoke()

WebMCPInvocation

Properties

result()

cancel()

WebMCPTool

Descriptor()

Invoke()

WebMCPInvocation

Descriptor()

Result()

Cancel()

​WebMCPTool

​Properties

​invoke()

​WebMCPInvocation

​Properties

​result()

​cancel()

​WebMCPTool

​Properties

​invoke()

​WebMCPInvocation

​Properties

​result()

​cancel()

​WebMCPTool

​Descriptor()

​Invoke()

​WebMCPInvocation

​Descriptor()

​Result()

​Cancel()

WebMCPTool

Properties

invoke()

WebMCPInvocation

Properties

result()

cancel()

WebMCPTool

Properties

invoke()

WebMCPInvocation

Properties

result()

cancel()

WebMCPTool

Descriptor()

Invoke()

WebMCPInvocation

Descriptor()

Result()

Cancel()