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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does disclose the return fields (channel name, description, subscriber count, thumbnail), which is useful, but it does not mention pagination behavior, result ordering, rate limits, or any access requirements. These are notable gaps for a search tool.

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

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

The description is a single efficient sentence that states the action, target resource, and key output fields. Every word earns its place, with no redundancy or filler.

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

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

The description covers the core purpose and return fields, and the schema fully documents both parameters. However, there is no output schema and the description does not explain pagination semantics beyond the schema default, nor does it route users to related channel-detail tools. This is adequate for a straightforward search tool but not exhaustive.

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

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

Schema description coverage is 100%, so both query and pages parameters are already documented in the schema. The description adds no additional parameter-level meaning beyond what the schema provides, which warrants the baseline score of 3.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: 'Search YouTube channels by keyword.' It clearly differentiates from sibling tools like search_youtube (likely videos) and youtube_channel_details (specific channel lookup) by focusing on channel search. The listed return fields further clarify the tool's scope.

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

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

The description implies the tool is used for keyword-based discovery of YouTube channels, but it does not explicitly state when to prefer this tool over siblings such as search_youtube or youtube_channel_details. There are no exclusions or alternative routing hints, leaving the agent to infer usage from the tool name and context.

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