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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds useful behavioral context by stating that only suggestions are returned, video/channel details are excluded, and pagination is unsupported; it also notes that suggested text can feed into video search. It does not discuss rate limits or result quantity, but with annotations present this is a strong disclosure.

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 compact and front-loaded, first stating what the tool returns and does not return, then giving routing guidance. Every clause adds useful information with no redundant restatement of the tool name.

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?

An output schema exists, so the description need not explain return values, and it still clarifies the output scope and lack of pagination. For a single-parameter read-only suggestion tool, the definition is nearly complete, though it could mention expected suggestion volume or language behavior.

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%, and the schema already explains that keyword is a search term or phrase and must not be a video link, channel link, ID, or pagination token. The description does not add further syntax or format detail about the keyword parameter, so the baseline score of 3 is appropriate.

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: retrieving YouTube search-box suggestions, and explicitly scopes it by saying it does not return video or channel details and does not support pagination. This distinguishes it from sibling tools such as youtube_search_videos and youtube_get_video_detail_by_url.

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?

It explicitly routes usage: use this for suggestions when there is no clear search term, use video search directly when a clear term exists, and use corresponding detail tools when a video or channel link exists. These are clear alternatives with conditions for selecting them.

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