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

Annotations already declare readOnlyHint and openWorldHint, so safety and open-world behavior need no restatement. The description adds that results are channel summaries and that page_token enables pagination, but says nothing about rate limits, result caps, or ordering. Useful but modest added context beyond the structured fields.

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?

A single dense sentence that front-loads the core action and appends the disambiguation clauses. Every clause carries routing value, though the packed structure with semicolons is slightly harder to parse than separate sentences would be.

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?

With a full output schema and fully described parameters, the description need not explain return values or parameter syntax. It covers purpose, routing, and pagination adequately; only deeper operational details like result limits are absent, which is a minor gap.

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 coverage is 100%, so both keyword and page_token are already documented with detailed descriptions, including the warning not to pass links, IDs, or tokens as keyword. The description adds only the general notion of pagination, which the schema covers more precisely; baseline 3 applies.

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?

States a specific verb and resource (search YouTube channels/creators by keyword) and explicitly contrasts itself with the two relevant siblings: channel-info-by-URL for existing channel pages and video search for videos. An agent can pick among these without opening any schema.

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?

Gives explicit routing rules: use this tool for keyword channel search, use the URL-based channel-info tool when a homepage link already exists, and use video search when looking for videos. Both the when-to-use and the when-not-to-use cases are covered.

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