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Playwright MCP

by nzjami
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TypeScript
Hybrid

browser_wait_for

Read-only

Pauses browser automation until specific text appears or disappears on a webpage, or for a set duration, to synchronize actions with page content changes.

Instructions

Wait for text to appear or disappear or a specified time to pass

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
timeNoThe time to wait in seconds
textNoThe text to wait for
textGoneNoThe text to wait for to disappear

Implementation Reference

  • src/tools/wait.ts:35-62 (handler)
    Handler function implementing the logic for 'browser_wait_for' tool: waits for time, text appearance, or disappearance using browser tab's Playwright page.
    handle: async (context, params, response) => {
  if (!params.text && !params.textGone && !params.time)
    throw new Error('Either time, text or textGone must be provided');

  const code: string[] = [];

  if (params.time) {
    code.push(`await new Promise(f => setTimeout(f, ${params.time!} * 1000));`);
    await new Promise(f => setTimeout(f, Math.min(30000, params.time! * 1000)));
  }

  const tab = context.currentTabOrDie();
  const locator = params.text ? tab.page.getByText(params.text).first() : undefined;
  const goneLocator = params.textGone ? tab.page.getByText(params.textGone).first() : undefined;

  if (goneLocator) {
    code.push(`await page.getByText(${JSON.stringify(params.textGone)}).first().waitFor({ state: 'hidden' });`);
    await goneLocator.waitFor({ state: 'hidden' });
  }

  if (locator) {
    code.push(`await page.getByText(${JSON.stringify(params.text)}).first().waitFor({ state: 'visible' });`);
    await locator.waitFor({ state: 'visible' });
  }

  response.addResult(`Waited for ${params.text || params.textGone || params.time}`);
  response.setIncludeSnapshot();
},
  • src/tools/wait.ts:23-33 (schema)
    Schema definition for the 'browser_wait_for' tool, including name, title, description, input schema with Zod validation, and type.
    schema: {
  name: 'browser_wait_for',
  title: 'Wait for',
  description: 'Wait for text to appear or disappear or a specified time to pass',
  inputSchema: z.object({
    time: z.number().optional().describe('The time to wait in seconds'),
    text: z.string().optional().describe('The text to wait for'),
    textGone: z.string().optional().describe('The text to wait for to disappear'),
  }),
  type: 'readOnly',
},
  • src/tools.ts:30-30 (registration)
    Import of the wait tool module that defines and exports the 'browser_wait_for' tool.
    import wait from './tools/wait.js';
  • src/tools.ts:51-51 (registration)
    Inclusion of tools from wait module (including 'browser_wait_for') into the central allTools array for global tool registration.
    ...wait,

Tool Definition Quality

B3.3/5.0
Behavior3/5

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

Annotations indicate readOnlyHint=true, destructiveHint=false, and openWorldHint=true, which already convey safety and flexibility. The description adds that it waits for text changes or time, but doesn't specify behavioral details like timeout behavior, concurrency, or error handling. No contradiction with annotations exists, so it meets the lower bar with minimal added context.

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 a single, efficient sentence that front-loads the core functionality without unnecessary words. Every part earns its place by covering the key actions (wait for text appear/disappear or time pass), making it highly concise and well-structured.

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 moderate complexity (3 parameters, no output schema) and rich annotations, the description is adequate but incomplete. It covers what the tool does but lacks details on return values, error conditions, or interaction with sibling tools, leaving gaps for the agent to navigate.

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?

Schema description coverage is 100%, with clear descriptions for time, text, and textGone parameters. The description mentions these concepts but doesn't add semantic details beyond the schema, such as how parameters interact (e.g., exclusive use) or default behaviors. Baseline 3 is appropriate given high schema coverage.

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 clearly states the tool's purpose as waiting for text to appear/disappear or for time to pass, which is specific and actionable. However, it doesn't explicitly differentiate from sibling tools like browser_wait_for_selector or browser_wait_for_timeout (if they existed), though among the actual siblings listed, it's distinct as the only waiting tool.

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 prerequisites (e.g., needing an active browser session) or compare to other waiting mechanisms in the browser toolset. This leaves the agent to infer usage from context 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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