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arc-control-mcp

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JavaScript
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Trusted Hover

trusted_hover
Idempotent

Trigger hover menus, tooltips, and :hover styles by moving a real mouse pointer over an element. Reports whether the browser considers the element hovered.

Instructions

Move a real mouse pointer over an element, so hover menus, tooltips and :hover styles appear. Needs the DevTools engine. Reports hoverApplied, whether the browser now considers the element hovered.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
nthNoWhich match to act on when several exist, 0-based
exactNoFor "text=", "label=" and "placeholder=" selectors, require the whole trimmed text to equal the label. No effect on CSS, ref= or role= selectors.
tab_idNoArc tab id from list_tabs. Omit to use this agent's current tab. A tool that changes a tab will not fall back to the tab the user is looking at, so pass this or call open_url first.
selectorYesCSS selector, or one of: "text=Some label" (visible text, case-insensitive substring, exact matches ranked first); "ref=e12" (a ref from snapshot, re-resolved if the page re-rendered); "role=button[name="Save"]" (ARIA or implicit role, name an exact match, or name~="sav" for a substring); "label=Email" (the control a label names); "placeholder=Search"

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv0.4.0

TDQS

A3.8/5.0
Behavior4/5

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

Annotations declare idempotent, non-destructive, open-world behavior, so the safety bar is partly covered. The description adds genuinely new behavioral detail: that it dispatches a 'real' pointer event rather than a synthetic one, requires the DevTools engine, and returns hoverApplied indicating whether the browser now considers the element hovered. That is meaningful extra context beyond the annotations.

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?

Three tight sentences: the action first, the engine prerequisite second, the return value last. No filler, and the most important information is front-loaded.

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?

With no output schema, the description usefully documents the return field (hoverApplied) and the engine requirement, and annotations cover the safety profile. The only remaining gap is guidance on when this beats the untrusted 'hover' tool.

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 all four parameters (nth, exact, tab_id, selector) are already fully documented in the schema. The description adds no syntax, format, or selector details beyond what the schema provides, so baseline 3 applies.

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?

States a specific verb and resource ('Move a real mouse pointer over an element') plus the observable effect (hover menus, tooltips, :hover styles). It is clear, but it never explicitly distinguishes itself from the sibling 'hover' tool, leaving the agent to infer the difference from the 'real mouse pointer'/'trusted' wording.

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

Usage Guidelines3/5

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

It gives one real prerequisite – 'Needs the DevTools engine' – which is useful usage context. However, it never says when to prefer this over the plain 'hover' sibling, nor any conditions or exclusions, so routing guidance is only implied.

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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