Playwright MCP

browser_tab_list

Read-only

Retrieve a list of open browser tabs for web automation and testing with Playwright MCP, enabling structured accessibility interactions without screenshots.

Instructions

List browser tabs

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Implementation Reference

src/tools/tabs.ts:20-35 (registration)

Full definition and registration of the 'browser_tab_list' tool, including schema, handler function, and capability.

const listTabs = defineTool({
  capability: 'core-tabs',

  schema: {
    name: 'browser_tab_list',
    title: 'List tabs',
    description: 'List browser tabs',
    inputSchema: z.object({}),
    type: 'readOnly',
  },

  handle: async (context, params, response) => {
    await context.ensureTab();
    response.setIncludeTabs();
  },
});

src/tools/tabs.ts:31-34 (handler)
The handler function for 'browser_tab_list' which ensures tab context and sets response to include tabs.
```
handle: async (context, params, response) => {
  await context.ensureTab();
  response.setIncludeTabs();
},
```

src/tools/tabs.ts:23-29 (schema)

Schema definition for 'browser_tab_list' tool: no input parameters, readOnly type.

schema: {
  name: 'browser_tab_list',
  title: 'List tabs',
  description: 'List browser tabs',
  inputSchema: z.object({}),
  type: 'readOnly',
},

Tool Definition Quality

B3.4/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the agent knows this is a safe, read-only operation that may return variable data. The description adds no behavioral context beyond what annotations provide (e.g., it doesn't specify what information is listed, format, or any limitations). There's no contradiction with annotations.

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 extremely concise at three words, front-loaded with the core action, and wastes no space. Every word ('List browser tabs') directly contributes to understanding the tool's purpose without redundancy or fluff.

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

Completeness3/5

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

Given the tool's low complexity (0 parameters, read-only), annotations cover safety, and no output schema exists, the description is minimally adequate. However, it lacks details on return values (e.g., tab titles, URLs, counts) or usage context, leaving gaps for an agent to fully understand how to interpret results.

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?

With 0 parameters and 100% schema description coverage, the schema fully documents the lack of inputs. The description doesn't need to compensate, and a baseline of 4 is appropriate since no parameter information is required. The description implicitly confirms no parameters are needed by not mentioning any.

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

Purpose4/5

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

The description 'List browser tabs' clearly states the verb ('List') and resource ('browser tabs'), making the purpose immediately understandable. However, it doesn't differentiate from sibling tools like 'browser_tab_select' or 'browser_tab_close', which would require mentioning it's specifically for listing/retrieving tab information rather than manipulating tabs.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention use cases like inventorying open tabs, checking tab status, or when to choose this over other browser tools. Without any context about timing or prerequisites, the agent must infer usage from the name alone.

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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