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Mehmoodqureshi

MCP Browser Extension

by Mehmoodqureshi
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TypeScript
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screenshot

Capture a browser page or element as a JPEG or PNG image for visual verification, with options for quality, scale, full page, selector, and frame.

Instructions

Capture a screenshot (page or element). Default is JPEG (quality 70) at CSS-pixel size, which is several times smaller than PNG and reads fine. Pass format:"png" for lossless, quality 1-100 for JPEG, scale 2 for device pixels on a Retina display or 0.5 to shrink.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
refNoElement ref from a snapshot
scaleNo
tabIdNoTab id (default: agent's tab)
formatNo
frameIdNoFrame id from frames_list
qualityNo
fullPageNo
selectorNoCSS selector (or pass ref)
allFramesNoAct on the first match in ANY frame (the element may be in an iframe)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.9.24
    • changedInput schema / properties / tabId / description
      Previous value: -"Tab id (default: active tab)"New value: +"Tab id (default: agent's tab)"
  2. Changed5 schema fields changedv0.9.5
    • changedInput schema / properties / allFrames / description
      Previous value: -"Search every frame of the tab and act on the first that matches - use when a selector should match but does not (the element is in an iframe)"New value: +"Act on the first match in ANY frame (the element may be in an iframe)"
    • changedInput schema / properties / frameId / description
      Previous value: -"Act inside this frame (ids come from frames_list)"New value: +"Frame id from frames_list"
    • changedInput schema / properties / ref / description
      Previous value: -"Element ref from a prior read (exactly one of selector|ref)"New value: +"Element ref from a snapshot"
    • changedInput schema / properties / selector / description
      Previous value: -"CSS selector (exactly one of selector|ref)"New value: +"CSS selector (or pass ref)"
    • changedInput schema / properties / tabId / description
      Previous value: -"Target tab id (defaults to the active tab)"New value: +"Tab id (default: active tab)"
  3. Changed3 schema fields changedv0.9.3
    • addedInput schema / properties / format
      Added value: +{
+  "enum": [
+    "jpeg",
+    "png"
+  ],
+  "type": "string"
+}
    • addedInput schema / properties / quality
      Added value: +{
+  "type": "number"
+}
    • addedInput schema / properties / scale
      Added value: +{
+  "type": "number"
+}
  4. Changed2 schema fields changedv0.7.0
    • addedInput schema / properties / allFrames
      Added value: +{
+  "description": "Search every frame of the tab and act on the first that matches - use when a selector should match but does not (the element is in an iframe)",
+  "type": "boolean"
+}
    • addedInput schema / properties / frameId
      Added value: +{
+  "description": "Act inside this frame (ids come from frames_list)",
+  "type": "number"
+}
  5. First observedv0.6.2

TDQS

B3.4/5.0
Behavior3/5

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

With no annotations, the description carries the full burden, and it does disclose useful defaults (JPEG q70, CSS-pixel size) and the rationale (smaller than PNG). It omits what the call returns (image payload, file path, base64), and says nothing about permissions, tab targeting side effects, or rate/large-page limits.

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

Conciseness4/5

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

Three tight sentences, front-loaded with the default behavior and size rationale before the overrides. No filler, though the format/quality/scale instructions are packed densely enough to require a careful read.

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?

For a 9-parameter tool with no annotations and no output schema, the description should explain the return payload and how ref/selector/fullPage/allFrames interact. It covers the imaging knobs well but leaves selection semantics and the response shape unaddressed.

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 coverage is 56%, and the description adds genuine meaning to three params: format tradeoffs, quality 1-100 as JPEG-only, and scale 2 for Retina / 0.5 to shrink. The remaining params (ref, selector, fullPage, allFrames, frameId, tabId) rely on terse schema strings, so the description only partially compensates for the coverage gap.

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?

States a specific verb and resource ('Capture a screenshot') and clarifies the two scopes it supports (page or element). It does not, however, distinguish itself from close siblings like snapshot, print_pdf, or get_html, which an agent would need to pick between.

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

Usage Guidelines3/5

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

Gives practical guidance on format/quality/scale tradeoffs, which implies the default choice. But it never says when to prefer this over snapshot or print_pdf, nor when an element vs full-page capture is appropriate, leaving the use-vs-alternative decision to inference.

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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