gecko-mcp

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screenshot

Read-only

Capture a tab as a PNG image. Targets the active tab or a specific browser. Optionally capture the full scrollable page.

Instructions

Take a screenshot of a tab and return it as a PNG image. Targets the active tab unless a browserId is given.

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": "screenshot"
  }
}

Input Schema

Name	Required	Description	Default
`browserId`	No	browserId of the tab to capture (from list_tabs). Defaults to the active tab.
`fullPage`	No	Capture the full scrollable page instead of just the viewport. Default: false.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2.2.4Jun 20, 2026

TDQS

A3.8/5.0

Behavior4/5

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

Annotations indicate read-only and open-world behavior, which the description supports. It adds behavioral context beyond annotations by specifying default targeting of the active tab and optional browserId, and the return format as PNG.

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 extremely concise with two sentences. The first sentence states the primary action and output, followed by a clarifying sentence about targeting. No wasted words.

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?

Given the tool's simplicity (two optional parameters, no output schema), the description covers the core behavior and parameter usage. It could mention the image encoding (e.g., base64) but is otherwise complete for typical use.

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 provides 100% coverage for the two parameters with clear descriptions. The description's mention of 'active tab unless browserId is given' is redundant with the schema, adding no new semantic value beyond what the schema already provides.

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 clearly states the tool takes a screenshot of a tab and returns it as a PNG image. It specifies the resource ('tab') and distinguishes from siblings like 'snapshot' by mentioning the output format and targeting behavior.

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 does not provide guidance on when to use this tool versus alternatives such as 'snapshot' or 'read_page'. It lacks explicit when-to-use or when-not-to-use criteria.

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