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DB-25

arc-control-mcp

Trusted Type

trusted_type

Type text into an input, textarea, or contenteditable using real events, so autocomplete and search-as-you-type fields react as if a user typed.

Instructions

Type into an input, textarea or contenteditable with real input events, so autocomplete dropdowns open and frameworks see genuine typing. Needs the DevTools engine. By default the text goes in as one insertText (fast, one trusted input event). per_key sends a real keydown, keypress, input and keyup for every character, which is what search-as-you-type boxes need. With no selector it types into the element that already has focus. Refuses a disabled, readonly or non-text element, and a field that does not take focus (nothing is typed then, rather than typing into another element). The result reports the field value afterwards (a password reports only its length).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
nthNoWhich match to act on when several exist, 0-based
textYesText to type
clearNoSelect the existing contents first so the typed text replaces them
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.
per_keyNoSend keydown, keypress, input and keyup for each character instead of one insertText
selectorNoField to focus first. CSS selector, "text=Label", or ref=, role=, label=, placeholder= as in click. Omit to type into the focused element.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv0.4.0

TDQS

A4.3/5.0
Behavior5/5

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

Annotations cover only safety hints, but the description adds substantial behavioral context: it requires the DevTools engine, refuses disabled/readonly/non-text fields and non-focusable elements (typing nothing rather than falling back to another element), and reports the resulting field value, with passwords reduced to length only.

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?

Six dense sentences, all carrying load, with purpose and the trusted-event distinction front-loaded. It is slightly long but no sentence is filler.

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?

With no output schema, the description supplies the missing return-value behavior (field value, password length) and covers the refusal/failure modes and engine prerequisite, so an agent has everything needed to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description goes further by explaining the rationale for per_key (search-as-you-type) and the no-selector focus behavior, which adds meaning beyond the schema's terse field descriptions.

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 (type) and resource (input/textarea/contenteditable) plus the distinguishing mechanism: real trusted input events that open autocomplete dropdowns and satisfy frameworks. It does not, however, name or differentiate itself from the sibling `type` and `fill` tools, leaving the agent to infer why trusted_type is needed over them.

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?

Gives concrete selection guidance: use per_key for search-as-you-type boxes, omit selector to type into the already-focused element, and it states the DevTools-engine prerequisite. What it omits is routing guidance against the sibling `type` and `fill` tools, so the agent must infer the alternative.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.