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

Annotations already cover the safety profile (readOnly, openWorld, non-destructive), so the description's real contribution is the billing model — one unit per result page fetched — and the cross-page collection behavior, both of which an agent cannot infer from structured fields. It omits anything about rate limits or failure behavior, keeping it short of a 5.

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?

Front-loaded with purpose, filters, and billing in that order, and the field enumeration is compact. The redundancy of stating 'returns the results as JSON' at the start and 'Returns JSON.' again at the end is wasted space.

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 field-by-field return-value enumeration is genuinely necessary and present, and the billing/paging notes cover the main operational risk. The only real gap is `proxy_country`, whose geo effect on results is never explained even though it can change what an agent gets back.

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 the baseline is 3. The description does add paging semantics for `max_results` ('collect ... across pages'), but it duplicates the enum values already in the schema, silently omits the `movie` type the schema allows, and never mentions `proxy_country`.

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 ('Searches YouTube for `query`') plus the return shape. It is clearly distinguishable from `youtube_transcript` by implication, but it never names the sibling or states that it returns listings rather than transcript/text content, so the differentiation is left to inference.

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 operational guidance ('filter with type and sort', 'keep max_results modest') but no when-to-use/when-not-to-use framing relative to alternatives such as youtube_transcript or google_search. Usage context is implied rather than stated.

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