usable-browser-agent-free

browser_snapshot

Capture a structured accessibility/DOM snapshot of the active Firefox tab, assigning stable refs to interactive elements for reliable automation. Re-run after page changes to refresh stale refs.

Instructions

Capture an accessibility/DOM snapshot of the active Firefox tab as a structured tree. Each interactive element gets a stable [ref=eN] handle. USE THIS to understand the page before acting, and re-run it after the page changes — refs become stale after navigation or DOM updates. If workflow-memory hints appear, call browser_workflow_recall before continuing.

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": "browser_snapshot"
  }
}

Input Schema

Name	Required	Description	Default
`maxNodes`	No	Max nodes to include (default 1500).

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.7.0Sep 9, 2026

TDQS

A4.4/5.0

Behavior4/5

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

No annotations are provided, so the description carries the full burden. It discloses a key behavioral trait—refs become stale after navigation/DOM updates—and implies the tool is a read-only snapshot. It could mention more about output format or side effects, but it covers the critical behavior for correct usage.

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 plus a conditional are tightly packed with useful information. The core purpose is front-loaded, followed by usage guidance and a cross-tool hint, with 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?

The tool has one optional parameter, no output schema, and no annotations. The description explains what the tool returns (structured tree with refs) and when to use it, which is sufficient for an agent to call it correctly. It doesn't detail the tree structure or maxNodes default, but these are minor gaps given the tool's simplicity.

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 only parameter (maxNodes) is already described in the schema. The description adds no extra meaning or context about how maxNodes affects the snapshot, so it stays at baseline 3.

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 captures an accessibility/DOM snapshot as a structured tree and introduces stable [ref=eN] handles. It distinguishes itself from siblings like browser_screenshot (visual capture) and browser_read_text (text extraction) by focusing on the interactive element tree with handles.

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

Usage Guidelines5/5

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

It explicitly says 'USE THIS to understand the page before acting' and instructs to re-run after page changes because refs become stale. It also gives a conditional to call browser_workflow_recall when workflow-memory hints appear, providing clear when-to-use and alternative routing.

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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