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Web Validator by DigestSEO

Web Validator by DigestSEO

by AKzar1el
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

Capture responsive screenshots

screenshot.capture
DestructiveIdempotent

Renders HTML files or URLs in a sandboxed Chromium browser, saving PNG screenshots to a specified directory for visual validation.

Instructions

Renders a local HTML file or HTTP(S) URL in a sandboxed local Chromium browser and writes PNG screenshots to the requested directory. Downloads the pinned headless browser on first use if it is not already cached. Existing matching files may be replaced.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "targetPath": "<targetPath>"
    },
    "name": "screenshot.capture"
  }
}

Input Schema

NameRequiredDescriptionDefault
outputDirNoDirectory where PNG screenshots will be written..mcp-validator/screenshots
viewportsNoOptional viewport definitions; defaults to desktop, tablet, and mobile sizes.
targetPathYesLocal HTML path or HTTP(S) URL to render.

Output Schema

NameRequiredDescriptionDefault
errorNo
screenshotsYes
outputDirectoryYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv1.1.0

TDQS

A3.7/5.0
Behavior4/5

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

The description adds meaningful behavioral details beyond the annotations: sandboxed Chromium, first-use browser download, and possible replacement of existing files. These details enrich the destructiveHint and openWorldHint annotations without contradicting them.

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?

Three well-ordered sentences: the core rendering/writing behavior, the runtime browser download behavior, and the destructive caveat. Every sentence earns its place with no filler or repetition.

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?

The schema and annotations cover parameter details, safety, and idempotency, while the description adds the non-obvious runtime facts: sandboxing, first-run browser download, and potential file replacement. Nothing essential for invoking the tool correctly is missing.

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 each parameter already has a clear description. The description's reference to the 'requested directory' adds little beyond the schema, so the baseline score of 3 is appropriate.

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 identifies the action ('writes PNG screenshots') and the resource ('local HTML file or HTTP(S) URL'), which distinguishes it from sibling tools focused on HTML, CSS, SEO metadata, and validation. However, it does not explicitly contrast itself with any sibling, so it stops just short of full differentiation.

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 states what inputs are accepted but gives no guidance about when to use screenshot.capture versus the sibling tools. There is no mention of use cases such as visual verification, or exclusions such as 'use html.local for DOM inspection instead.'

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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