---
title: "Discover WebMCP tools across the browser"
method: GET
path: "/browsers/{id_or_name}/webmcp/tools"
tags: ["Browser WebMCP"]
---

# Discover WebMCP tools across the browser

`GET /browsers/{id_or_name}/webmcp/tools`

## Request

- Base URL: `https://api.onkernel.com`
- URL: `https://api.onkernel.com/browsers/{id_or_name}/webmcp/tools`
- Auth: HTTP bearer

Returns a snapshot of native and custom WebMCP tools available across every open tab and
embedded frame in the browser. Each tool includes an opaque tool_ref for invoking that exact
live registration, nested tool metadata, and source information. Custom tools include their
generated ID, namespace, and CDP target_id in source. Tools disappear when their document
closes or navigates away. Use exclude_custom to return only page-provided tools.

## Path parameters

- `id_or_name` string, required

## Query parameters

- `exclude_custom` boolean

## Response `200`

Current browser-wide WebMCP tool snapshot

- WebMCPToolsResponse
  - `tools` WebMCPTool[], required
    - `source` WebMCPToolSource, required
      - `custom` WebMCPCustomToolSource
        - `id` string, required
        - `namespace` string, required
      - `frame` WebMCPToolFrame, required
        - `frame_id` integer, required: Monotonically increasing identifier for this embedded frame during the current browser process.
        - `url` string, required: Current frame URL with the fragment omitted.
      - `page_title` string, required: Current title of the top-level page.
      - `page_url` string, required: Current URL of the top-level page with the fragment omitted.
      - `tab_id` integer, required: Monotonically increasing identifier for the tab during the current browser process.
      - `target_id` string: CDP target ID for a custom tool's registration tab; omitted for page-provided tools.
      - `window_id` integer, required: Monotonically increasing identifier for the browser window during the current browser process.
    - `tool` WebMCPToolMetadata, required: Tool metadata follows the [MCP Tool definition](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#tool) and the [WebMCP RegisteredTool definition](https://webmachinelearning.github.io/webmcp/#dictdef-registeredtool). outputSchema is optional for page and custom tools.
      - `annotations` WebMCPToolAnnotations: Tool-provided behavioral hints from the [MCP tool specification](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#tool) and the [WebMCP ToolAnnotations definition](https://webmachinelearning.github.io/webmcp/#dictdef-toolannotations). These hints are untrusted and are not enforced by Kernel.
        - `autosubmit` boolean
        - `consequentialHint` boolean
        - `destructiveHint` boolean
        - `idempotentHint` boolean
        - `openWorldHint` boolean
        - `readOnlyHint` boolean
        - `untrustedContentHint` boolean
      - `description` string, required
      - `inputSchema` object, required
      - `name` string, required
      - `outputSchema` object
      - `title` string
    - `tool_ref` string, required: Opaque reference for invoking this exact live registration. It becomes invalid when its document or browser process is replaced.

## Other responses

- `404`: Resource not found
- `500`: Internal Server Error
- `default`: Error returned by the browser or its proxy

## Changes

- **2026-09-25** `743e00322e20`: 3 breaking, 1 warning, 4 info
  - removed the required property `tools/items/description` from the response with the `200` status
  - removed the required property `tools/items/input_schema` from the response with the `200` status
  - removed the required property `tools/items/name` from the response with the `200` status
  - removed the optional property `tools/items/annotations` from the response with the `200` status
  - …4 more
- **2026-09-03** `8a0b0be14e94`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/onkernel/apis/kernel-api/changes/browsers/:id_or_name/webmcp/tools/get.md)

---

[API](https://skmtc.dev/onkernel/apis/kernel-api.md) - [All operations](https://skmtc.dev/onkernel/apis/kernel-api/llms.txt) - [OpenAPI document](https://skmtc.dev/onkernel/apis/kernel-api/revisions/0f6cf4f58fe6?raw)