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puppeteer_screenshot

Capture screenshots of web pages or specific elements using browser automation on Linux display servers. Specify dimensions and CSS selectors for precise captures.

Instructions

Take a screenshot of the current page or a specific element

Input Schema

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

Implementation Reference

  • Switch case implementing the puppeteer_screenshot tool: sets viewport, takes screenshot of page or selected element, stores it, and returns image content.
    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: ${args.selector}` : "Screenshot failed",
          }],
          isError: true,
        };
      }
      screenshots.set(args.name, screenshot);
      server.notification({
        method: "notifications/resources/list_changed",
      });
      return {
        content: [
          {
            type: "text",
            text: `Screenshot '${args.name}' taken at ${width}x${height}`,
          },
          {
            type: "image",
            data: screenshot,
            mimeType: "image/png",
          },
        ],
        isError: false,
      };
    }
  • Input schema for puppeteer_screenshot tool defining parameters: name (required), selector, width, height.
    {
      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"],
      },
    },
  • index.ts:447-449 (registration)
    Registration of the tools list via ListToolsRequestSchema handler, which returns the TOOLS array including puppeteer_screenshot.
    server.setRequestHandler(ListToolsRequestSchema, async () => ({
      tools: TOOLS,
    }));
  • index.ts:451-451 (registration)
    Registration of the CallToolRequestSchema handler, which dispatches to handleToolCall implementing puppeteer_screenshot.
    server.setRequestHandler(CallToolRequestSchema, async (request) => handleToolCall(request.params.name, request.params.arguments ?? {}));
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the action but doesn't describe what happens: e.g., does it save the screenshot to a file, return it as data, or require specific permissions? It omits details like potential side effects (e.g., might pause execution), error conditions, or output format, which are critical for a tool with no structured behavioral hints.

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 directly states the tool's purpose without unnecessary words. It's front-loaded with the core action and target, making it easy to parse. Every part of the sentence earns its place by clarifying scope ('current page or a specific element').

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 complexity of a screenshot tool with no annotations and no output schema, the description is incomplete. It doesn't address key aspects: what the output is (e.g., file path, base64 data), how errors are handled, or behavioral traits like whether it waits for page load. For a tool that interacts with a browser and produces visual data, more context is needed to ensure correct usage.

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 parameter descriptions in the schema (e.g., 'CSS selector for element to screenshot', default values for width/height). The description adds minimal value beyond the schema by implying 'current page' as a default when no selector is provided, but it doesn't explain parameter interactions or provide examples. Baseline 3 is appropriate since the schema does the heavy lifting.

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 action ('Take a screenshot') and target ('current page or a specific element'), which is specific and actionable. It distinguishes from sibling tools like puppeteer_click or puppeteer_navigate by focusing on capturing visual output rather than interaction or navigation. However, it doesn't explicitly differentiate from all siblings (e.g., puppeteer_evaluate might also capture data).

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., requires a page to be loaded), exclusions, or comparisons with other screenshot or capture methods. With siblings like puppeteer_evaluate that might retrieve page content differently, this lack of context leaves the agent guessing.

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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