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Chrome Browser Control

Chrome Browser Control

by vKongv
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TypeScript
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Visible page snapshot

visible_snapshot

Get a viewport-aware snapshot of visible page elements, including refs, labels, roles, bounds, and scroll metadata, to interact with the current browser view.

Instructions

Return a viewport-aware snapshot with visible/intersecting elements, refs, labels, roles, bounds, and scroll metadata. Iframe bounds use frameViewport coordinates.

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": "visible_snapshot"
  }
}

Input Schema

NameRequiredDescriptionDefault
limitNo
tabIdNoOptional Chrome tab id. Defaults to the claimed session tab, then the active tab.
documentIdNoExact frame document id returned by list_frames. Omit to target the current top document.
sessionTabIdNoOptional claimed tab session id returned by claim_tab.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.4.0

TDQS

B3.3/5.0
Behavior3/5

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

With no annotations, the description must disclose behavioral traits. It adds useful context about viewport-awareness and that iframe bounds use frameViewport coordinates, which is a specific coordinate system note. However, it does not mention read-only nature (though implied), potential performance costs, pagination, or what happens when no visible elements exist. It is not misleading, but it leaves some behavior unspecified.

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 two sentences with no wasted words. The primary function is front-loaded in the first sentence, and the coordinate detail is a concise second sentence. Every word adds value, making it an efficient and well-structured description.

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?

The tool has four optional parameters and no output schema, so the description must explain what the agent receives and any constraints. It lists the returned content types and notes the coordinate system, which is helpful. However, it lacks usage context (when to prefer this over 'snapshot'), does not mention any limits or pagination, and does not describe the response format. Given the moderate complexity and lack of output schema, the description is adequate but not fully complete.

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 75% (three of four parameters have descriptions; 'limit' does not). The description itself adds no parameter-specific meaning, but it is not required to since most parameters are already documented in the schema. The missing 'limit' description is a gap, but the description does not attempt to compensate. Given moderate coverage, the baseline is a 3.

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 states the tool returns a viewport-aware snapshot and enumerates its contents (visible/intersecting elements, refs, labels, roles, bounds, scroll metadata). The verb 'Return' and resource 'viewport-aware snapshot' are specific. It distinguishes itself from a generic 'snapshot' by emphasizing viewport-awareness, though it does not explicitly name the sibling 'snapshot' tool or contrast them.

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 provides no guidance on when to use this tool versus alternatives like 'snapshot', 'query_elements', or 'extract_elements'. It does not mention use cases, exclusions, or conditions that would select this tool over others. An agent would have to infer usage from the tool name and description alone, which is insufficient given the sibling list.

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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