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 context: it mentions 'only returns video results', filtering support, page_token pagination, and the exclusion of playlist links. These behavioral traits go beyond the annotations and are useful for the agent. Since annotations cover the base safety, a 4 is appropriate—it adds meaningful context without needing to repeat the read-only property.

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?

Two sentences, purpose first, then usage guidance and limitations. No redundant phrasing, each clause earns its place. The description is front-loaded with the core action and scope, and the usage guidance follows naturally. It is concise without sacrificing substance.

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?

Given the tool has 6 parameters, one required, 100% schema coverage, and an output schema, the description covers everything an agent needs: when to use, when not, pagination behavior, and limitations (playlist links). The output schema handles return structure, so nothing is missing. The description is complete for correct invocation and routing.

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 each parameter (keyword, sort_type, page_token, video_type, duration_range, publish_time_range) has detailed descriptions in the schema, including enums, defaults, and explicit instructions (e.g., not to modify page_token, what not to pass as keyword). The overall description adds no extra parameter-specific meaning beyond what the schema already provides. With coverage at 100%, the baseline of 3 is appropriate; the description does not need to compensate.

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 clearly states the verb 'search', the resource 'YouTube public videos', and the scope 'only returns video results'. It distinguishes itself from video detail, comment, and channel tools by explicitly listing what to use when the user already has a link or channel. This is unambiguous and separates it from siblings.

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?

Provides explicit when-to-use: 'when the user needs to find videos by search term'. It gives exclusions: 'if the user already has a video, Shorts, or youtu.be link, use video detail/comment tools; if they have a channel homepage link, use channel profile/posted videos tools'. It also states playlist links are not supported as search input. This is thorough routing that needs no inference.

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