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Chrome Dialog MCP

Chrome Dialog MCP

by mikebeaton
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Local

start_dialog_capture

Begins a one-time observation window before an action that may open a browser JavaScript dialog, so you can later retrieve and handle the captured OK/Cancel or prompt response.

Instructions

Start a single-use observation interval in the browser_token session immediately before an anticipated dialog-producing operation. Requires a connected observer and no already-pending dialog in that session. Only if Windows Computer Use refuses a click with "coordinate input geometry is unavailable": require get_dialog_status(browser_token) to return no_dialog, call get_window_state on that same window with include_screenshot: true and include_text: true, choose the target from the fresh observation and retry the refused click once. Keep any already-armed capture_id. Keep capture_id with browser_token. Perform the expected operation without Computer Use capture afterward, then call get_captured_dialog. Every opening in that Chrome instance counts, including other tabs/windows and dialogs that close or are replaced; separate managed sessions do not count.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "browser_token": "<browser_token>"
    },
    "name": "start_dialog_capture"
  }
}

Input Schema

NameRequiredDescriptionDefault
browser_tokenYesPrivate capability token for this managed browser session; use the token returned by launch_chrome.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.1

TDQS

A4.5/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full behavioral burden and does so well: it states the capture is single-use, requires a connected observer and no pending dialog, and explains that every opening in the Chrome instance counts, including other tabs/windows and replaced dialogs, while separate managed sessions do not. It also specifies capture_id retention and the expected follow-up behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The purpose is front-loaded and most sentences add actionable information about prerequisites, fallback behavior, and capture scope. The description is dense and somewhat long for a one-parameter tool, but it avoids obvious redundancy and keeps the critical instructions together.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with no output schema and no annotations, the description covers timing, prerequisites, failure handling, capture scope, and the follow-up call get_captured_dialog. It does not explicitly describe the return value or failure response of start_dialog_capture itself, but it provides enough context to invoke and use the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There is only one parameter, browser_token, and schema description coverage is 100%, so the schema already supplies the parameter syntax and meaning. The description reinforces the session scope but does not add new semantic detail about the parameter beyond what the schema provides.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The first sentence states a specific verb and resource: starting a single-use observation interval in the browser_token session immediately before a dialog-producing operation. It distinguishes the action from follow-up siblings by directing the agent to call get_captured_dialog afterward and to use only the specified fallback path for Windows Computer Use failures.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives explicit timing guidance (immediately before an anticipated dialog-producing operation) and prerequisites (connected observer, no already-pending dialog). It also names alternatives and checks: get_dialog_status for no_dialog, get_window_state for fresh observation, and get_captured_dialog after the operation.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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