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arc-control-mcp

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Wait For Load

wait_for_load
Read-onlyIdempotent

Poll a tab until its document finishes loading and is ready after a navigation action; checks Arc's loading flag and document.readyState, with timeout and optional URL match.

Instructions

Poll until a tab has finished loading and the document is ready. Use after an action that triggers navigation. Checks Arc's own loading flag as well as document.readyState. Arc does not answer scripts while a tab loads, so the flag is what lets a slow server or a hung iframe show up as ready 'loading' on the timeout, instead of as a stalled call. If the load never ends, stop_loading ends it.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
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.
timeout_msNoGive up after this long. Capped at 30000ms so the call cannot outlive a client's request timeout. To wait longer, call this again.
url_containsNoAlso wait until the url contains this substring

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv0.4.0
    • 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."
    • changedInput schema / properties / timeout_ms / description
      Previous value: -"Give up after this long. Capped at 30000ms, because a longer call is killed by the client before it can answer. To wait longer, call wait_for_load again: repeated short waits each hand back a real readyState and url, which one long wait does not."New value: +"Give up after this long. Capped at 30000ms so the call cannot outlive a client's request timeout. To wait longer, call this again."
  2. First observedv0.3.0

TDQS

A4.3/5.0
Behavior5/5

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

Goes well beyond the readOnly/idempotent annotations by explaining why polling is needed (Arc does not answer scripts while a tab loads), what the timeout actually reports ('loading' rather than a stalled call), and which sibling terminates a hung load. That is exactly the behavioral context annotations cannot carry.

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?

Front-loaded with the core behavior and the usage trigger in the first two sentences. The loading-flag explanation is valuable but slightly long; overall the sentences earn their place, though the last clause could be tightened.

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 and a straightforward read-only poll, the description covers the mechanism, the failure mode, and the escape route. It could state what a returned result looks like on success vs. timeout, but that is a minor gap for this operation.

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 three parameters (tab_id, timeout_ms, url_contains) are already documented in the schema, including the 30000ms cap and the fallback rule. The description adds only indirect hints about timeout behavior, so 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?

Specific verb+resource: 'poll until a tab has finished loading and the document is ready.' It names the exact conditions checked (Arc's loading flag, document.readyState), which distinguishes it from siblings like wait_for_selector and wait_for_text.

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 a clear trigger ('Use after an action that triggers navigation') and names the escape hatch ('If the load never ends, stop_loading ends it'). It doesn't explicitly contrast with wait_for_text/wait_for_selector, so it stops short of full 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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