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

The annotations already declare readOnly, idempotent, openWorld and non-destructive behavior, so the safety profile is covered. The description adds value beyond that with the return shape (titles, channels, durations, links) and the pagination invariant that the query/language/region must not change across cursor calls — a non-obvious constraint. It does not mention result caps or rate limits.

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, zero filler, with purpose front-loaded and the pagination constraint second. Every clause carries information an agent needs.

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 no output schema, the description compensates by naming the returned fields, and it explains the cursor-based pagination model. Minor gaps remain: no indication of typical result counts, ordering, or behavior when the query has no matches, which matter for a search tool.

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 all four parameters are already documented with formats and patterns. The description restates the cursor invariance rule that the schema already states verbatim, adding no new meaning to query, region or language. Baseline 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?

States a specific verb and resource ("Finds YouTube videos from a text query") and even names the returned fields, so an agent can distinguish it from get_video_info or transcribe_video. It stops short of explicitly contrasting with those siblings, but the 'text query' framing makes the distinction inferable.

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 pagination rule ("Additional pages use the opaque nextCursor; the query, language and region must remain unchanged") gives real operational guidance for repeated calls. However, there is no statement of when to choose this tool over get_video_info, get_usage, or transcribe_video, and no exclusions or prerequisites.

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