Skip to main content
Glama
Sign In
invisible-playwright-mcp

invisible-playwright-mcp

by solver492
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

browser_list

Read-only

Reports which browsers are open, each page and URL, and which browser your last command used, so you can confirm the active target before acting; it starts nothing.

Instructions

Which of the two browsers are open, where each one is, and which one you are working in.

Answers JSON: focus, the browser your last command acted in, or "" when none is open; note, which says how many are open and that a command naming no browser goes to main; and browsers - each row id, url (the page it is on) and urls (every page it holds, which is more than one only when a site opened one). Only open browsers are listed, so every row is one you can act on.

Starts nothing: it reports what is open, so asking is free.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "browser_list"
  }
}

Input Schema

NameRequiredDescriptionDefault

No arguments

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.70.2

TDQS

A4.7/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: it reports only open browsers, explains the 'focus' field, and clarifies that it starts nothing. This goes beyond the annotations by explaining the tool's side-effect-free nature and output semantics.

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

Conciseness5/5

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

The description is well-structured and front-loaded: it starts with the core question the tool answers, then details the JSON output, and ends with a clear note about side effects. Every sentence adds value, and the formatting with backticks and line breaks improves readability.

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

Completeness5/5

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

Given the tool has no parameters and an output schema exists, the description is complete. It explains the output fields, the meaning of 'focus', the behavior with multiple tabs, and the side-effect-free nature. An agent has everything needed to call and interpret this tool correctly.

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

Parameters4/5

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

The tool has zero parameters, so the schema provides no parameter semantics. The description compensates by explaining the output structure (focus, note, browsers with id, url, urls), which is the only meaningful semantic content for a parameterless tool. Baseline 4 is appropriate.

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 description clearly states the tool's purpose: it reports which of the two browsers are open, their locations, and which one the agent is working in. It distinguishes itself from siblings by focusing on listing/status rather than actions like navigate or close.

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 explicitly says when to use it: to check what is open and which browser is the focus. It also notes that it starts nothing and is free to call, implying it's safe to use as a status check. It doesn't explicitly name alternatives, but the sibling list makes it clear this is the listing/status tool.

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

Deploy Server

Other Tools