web_eval

Web automation · macOS · Windows

Effect: execute (strongest supported action). Status: gated.

Gated means the tool requires an installed app, a connected account, permission, or runtime availability. Check those requirements on the listed platform before using it.

macOS

Purpose

Runs arbitrary JavaScript in a web session and returns the last expression's value, which must be a plain JSON value (async code is not awaited: return JSON.stringify(...) or store the result and read it in a second call). Requires confirm=true; without it you get a preview of the code and nothing runs. Disabled when LMCP is in read-only mode. POWER-USER tool — a page could feed malicious code, so prefer web_find / web_read / web_extract for normal use.

Required inputs

js — JavaScript to evaluate on the page; the last expression's value is returned.

Permissions and confirmation

Explicit confirmation parameter: inspect the schema and tool description before any real call. The documentation example keeps confirm false. Obtain user authorization before performing the action.

Use only the apps, accounts and resources authorized by the user on this platform. Consult this tool's platform-specific description for its connection and permission requirements; this catalog does not assert additional OAuth scopes or OS entitlements.

Full input schema — macOS

{
  "properties": {
    "confirm": {
      "description": "Must be true to run the code. Without it, returns a preview and runs nothing.",
      "type": "boolean"
    },
    "js": {
      "description": "JavaScript to evaluate on the page; the last expression's value is returned.",
      "type": "string"
    },
    "session": {
      "description": "Session name (default 'default').",
      "type": "string"
    }
  },
  "required": [
    "js"
  ],
  "type": "object"
}

Documentation example

Do not execute this example. These concrete inputs refer to a fictional demonstration dataset. Resolve real handles and obtain user authorization before any real call.

{
  "confirm": false,
  "js": "document.title",
  "session": "demo-browser"
}

Windows