OmniSnap MCP

The page at three widths

capture_matrix

Read-only

Captures a full page at mobile, tablet, and desktop widths and returns the screenshots side by side in one image for quick responsive review.

Instructions

Captures the full page at phone, tablet and desktop widths and returns them side by side in one image. Use it to check a responsive change in a single look, rather than three captures you have to hold in mind at once.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "capture_matrix"
  }
}

Input Schema

Name	Required	Description	Default
`widths`	No	Defaults to all three: 375, 768 and 1440.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.2.3Nov 11, 2026

TDQS

A4/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuine value by disclosing the return shape (a single composite image with widths side by side), but says nothing about failure modes, ordering guarantees, or what happens if only a subset of widths is requested.

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?

Two sentences, front-loaded with what it does, followed by the decision rule. No filler and no restatement of the tool name or titles.

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

Completeness4/5

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

For a one-optional-parameter, no-output-schema tool this is nearly complete — the description itself explains the returned artifact, which compensates for the absent output schema. Minor gap: nothing about how the requested widths are ordered or what happens with partial subsets.

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 100% and the single width parameter already carries its default and pixel values, so the schema does the heavy lifting. The description reinforces which three widths exist but adds no syntax or behavior beyond the schema — the baseline 3 applies.

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?

States a specific verb and resource — capturing the full page at phone, tablet and desktop widths — and pins down the distinctive output (all three side by side in one image). That output shape cleanly separates it from a plain single-page capture sibling.

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

Usage Guidelines4/5

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

Gives a clear when-to-use condition: checking a responsive change in a single look, contrasted with the alternative of three separate captures. It stops short of naming the actual sibling tools (e.g. capture_page) or stating when-not to use it, so it is strong but not fully explicit routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.