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freema

Firefox DevTools MCP

by freema

take_snapshot

Capture a stable DOM snapshot of the current page, with options to limit depth, include attributes or text, and scope to a specific CSS selector. Use after navigation to get updated snapshots.

Instructions

Capture DOM snapshot with stable UIDs. Retake after navigation.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
maxLinesNoMax lines (default: 100)
includeAttributesNoInclude ARIA attributes (default: false)
includeTextNoInclude text (default: true)
maxDepthNoMax tree depth
includeAllNoInclude all visible elements without relevance filtering. Useful for Vue/Livewire apps (default: false)
selectorNoCSS selector to scope snapshot to specific element (e.g., "#app")
Behavior2/5

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

No annotations provided, so the description must cover behavioral traits. It mentions 'stable UIDs' and need to retake after navigation, but omits side effects, safety (read-only?), or error conditions. Insufficient for a tool with 6 parameters.

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 purpose and key guidance. No filler words.

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 description is minimal but covers the core purpose. With 6 parameters and no output schema, more context (e.g., what 'stable UIDs' enable for other tools) would improve completeness.

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 baseline is 3. The description adds no parameter-specific meaning 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 clearly states the action ('Capture DOM snapshot') and the specific output ('with stable UIDs'), distinguishing it from sibling tools like screenshot or clear_snapshot.

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?

Provides a direct usage hint: 'Retake after navigation'. Lacks explicit when-not-to-use or alternatives, but the hint is valuable and clear.

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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