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Puppeteer MCP Server

by cploujoux
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puppeteer_screenshot

Capture webpage or element screenshots with customizable dimensions using CSS selectors, enabling precise visual extraction for browser automation tasks.

Instructions

Take a screenshot of the current page or a specific element

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
heightNoHeight in pixels (default: 600)
nameYesName for the screenshot
selectorNoCSS selector for element to screenshot
widthNoWidth in pixels (default: 800)

Implementation Reference

  • index.ts:182-224 (handler)
    Handler for puppeteer_screenshot tool: sets viewport, captures screenshot of page or specified element, stores it in screenshots map, notifies resource change, returns success message and image content or error if failed.
    case "puppeteer_screenshot": {
  const width = args.width ?? 800;
  const height = args.height ?? 600;
  await page.setViewport({ width, height });

  const screenshot = await (args.selector
    ? (await page.$(args.selector))?.screenshot({ encoding: "base64" })
    : page.screenshot({ encoding: "base64", fullPage: false }));

  if (!screenshot) {
    return {
      content: [
        {
          type: "text",
          text: args.selector
            ? `Element not found: ${args.selector}`
            : "Screenshot failed",
        },
      ],
      isError: true,
    };
  }

  screenshots.set(args.name, screenshot as string);
  server.notification({
    method: "notifications/resources/list_changed",
  });

  return {
    content: [
      {
        type: "text",
        text: `Screenshot '${args.name}' taken at ${width}x${height}`,
      } as TextContent,
      {
        type: "image",
        data: screenshot,
        mimeType: "image/png",
      } as ImageContent,
    ],
    isError: false,
  };
}
  • index.ts:30-52 (schema)
    Input schema definition for puppeteer_screenshot tool within the TOOLS array, specifying required 'name' and optional 'selector', 'width', 'height' parameters.
    {
  name: "puppeteer_screenshot",
  description: "Take a screenshot of the current page or a specific element",
  inputSchema: {
    type: "object",
    properties: {
      name: { type: "string", description: "Name for the screenshot" },
      selector: {
        type: "string",
        description: "CSS selector for element to screenshot",
      },
      width: {
        type: "number",
        description: "Width in pixels (default: 800)",
      },
      height: {
        type: "number",
        description: "Height in pixels (default: 600)",
      },
    },
    required: ["name"],
  },
},

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

B3/5.0
Behavior2/5

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

No annotations are provided, so the description carries full burden. It does not disclose what happens to the screenshot (e.g., saved to disk, returned as base64), nor any side effects or permissions needed.

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

Conciseness3/5

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

The description is a single sentence, which is concise, but it lacks essential context such as output format or usage details. It is under-specified.

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

Completeness2/5

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

Given the lack of output schema and annotations, the description should explain what happens with the screenshot. It fails to mention return value or storage, making it incomplete.

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%, and the description adds no additional meaning beyond the schema. Baseline score of 3 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 takes a screenshot of the current page or a specific element, with a specific verb and resource. It differentiates from sibling tools like puppeteer_navigate or puppeteer_click.

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?

No guidance on when to use this tool versus alternatives, no preconditions, and no mention of when to capture a full page versus an element.

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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