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

Annotations already carry the safety profile (readOnly, destructive=false, openWorld, idempotent), so the description's main additions are the input-format flexibility and the 20-item cap. It does not disclose rate limits, auth requirements, or pagination behavior, which matters for an open-world external API call. With annotations covering safety, this is adequate but not rich.

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?

Four tight sentences: purpose, input formats, return shape, then purpose/alternative routing. Front-loaded and free of filler; every clause carries information.

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 return-field explanation is a bonus rather than a requirement, and annotations cover the safety profile. For a filtered read-only list tool, the description covers everything an agent needs to invoke it correctly.

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 parameters are already documented, including the maxRows 1-20 cap. The description's handle/URL examples mirror the schema text rather than adding new meaning. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('List the latest videos on one YouTube channel') and scopes it to a single channel with accepted identifier formats. It explicitly distinguishes itself from youtube_search, so an agent can route correctly without opening a 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 an explicit use case ('audit a creator or competitor channel') and names the alternative with its selection condition ('To search all of YouTube by keyword use youtube_search'). Nothing is left to inference.

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