OmniSnap MCP

Capture one element

capture_element

Read-only

Capture a screenshot of a single page element using its CSS selector to inspect one component instead of the full page.

Instructions

Screenshots a single element, given a CSS selector. Cheaper and far easier to reason about than a full page when the question is about one component.

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_element"
  }
}

Input Schema

Name	Required	Description	Default
`element`	No	A number from the most recent annotate_interactive on this tab. Easier and safer than retyping a selector.
`selector`	No	A CSS selector for the element to capture.

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 a useful cost/complexity trait ('cheaper and far easier to reason about'), but says nothing about return form, scrolling the element into view, waiting for render, or failure on hidden/absent elements.

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, verb-first, zero padding. The scope contrast in the second sentence earns its place by aiding tool selection.

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 simple two-parameter capture tool with full schema coverage and adequate annotations, this is nearly sufficient. The one real gap is that there is no output schema and the description does not say what a caller receives back (image content vs. a path or handle).

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%, so both parameters are already well documented, including that 'element' is an index from annotate_interactive. The description only references the CSS selector path and never mentions the safer index-based alternative, adding little beyond the schema.

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 opens with a specific verb and resource ('Screenshots a single element') and immediately narrows scope ('given a CSS selector'). The contrast with 'a full page' lets an agent distinguish it from capture_page without inspecting either schema.

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?

It states a clear selection condition: use this 'when the question is about one component', and implicitly the opposite for page-level questions. It stops short of naming capture_page or capture_matrix explicitly, so routing still requires a small inference.

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