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arc-control-mcp

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Select Option

select_option

Choose an option in a select element by exact value or visible label. Fails if disabled or unmatched, lists available options, then waits for the page to settle.

Instructions

Choose an option in a select element, by exact option value or exact visible label. A disabled select or option fails rather than being set. When nothing matches, the failure lists the options that do exist, so the next call can pick a real one. On success it waits for the page to go quiet and reports settledMs (and settled false if the DOM was still changing at the cap), so the next read sees the result of the action.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
optionYesOption value or visible text, matched exactly after trimming
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, ref=e12 or role=combobox[name="Country"] for the <select>. "text=" cannot reach a select element.
settle_msNoAfter acting, wait until the page's DOM has been quiet for this many ms, then report settledMs. 0 skips the wait. The whole wait is capped at 1500ms; a page that never goes quiet reports settled false.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed3 schema fields changedv0.4.0
    • changedInput schema / properties / selector / description
      Previous value: -"CSS selector for the <select>. \"text=\" cannot reach a select element, so use a CSS selector here."New value: +"CSS selector, ref=e12 or role=combobox[name=\"Country\"] for the <select>. \"text=\" cannot reach a select element."
    • addedInput schema / properties / settle_ms
      Added value: +{
+  "default": 300,
+  "description": "After acting, wait until the page's DOM has been quiet for this many ms, then report settledMs. 0 skips the wait. The whole wait is capped at 1500ms; a page that never goes quiet reports settled false.",
+  "maximum": 1500,
+  "minimum": 0,
+  "type": "number"
+}
    • changedInput schema / properties / tab_id / description
      Previous value: -"Arc tab id from list_tabs. Omit to use this agent's current tab, falling back to whatever tab is active in Arc."New value: +"Arc 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."
  2. First observedv0.3.0

TDQS

A4.2/5.0
Behavior5/5

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

Annotations only cover the safety profile (readOnly=false, destructive=false, openWorld=true). The description adds real behavioral context: disabled elements fail, a failed match enumerates the available options for the next call, success waits for the DOM to settle, and settledMs/settled=false are reported so the next read is accurate.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Four sentences, front-loaded with the purpose and then failure/settle semantics. Mostly efficient, though the settle wait and settledMs reporting are largely duplicative of the settle_ms schema description.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, so the description carries the return-value burden and does so: it explains settledMs, the settled=false cap condition, and the options-listing failure payload. For a 4-param, non-read-only action this is 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 100%, so the schema already documents selector, tab_id, option and settle_ms in detail. The description restates the option-matching rule and the settle/wait behavior rather than adding new meaning, so the baseline 3 applies.

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?

States a specific verb and resource ('Choose an option in a select element') and pins down the matching basis (exact value or exact visible label). That scope distinguishes it from the generic fill/type siblings, which cannot target a <select>.

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?

Usage is strongly implied by the need to set a select element, and the description notes that disabled selects/options fail rather than being set. However, it never explicitly names an alternative (e.g. fill/type) or states when not to use this tool; the 'text=' limitation only appears in the schema, not the description.

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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