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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description usefully adds the 50-video cap and the 20-newest default, but says nothing about auth/permission requirements, rate limiting, or data freshness (how quickly a newly posted video appears), which matter for an analytics call.

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, no filler, with the return payload front-loaded before the videoIds/default note. The metric enumeration is long but each item is a concrete returned field that helps the agent decide relevance.

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 partially compensates by naming the returned metrics and the default/largest batch sizes. All five parameters are schema-documented, so the remaining gaps (date-window semantics, error behavior when >50 ids, profile/account interactions) are modest rather than crippling.

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, but the description earns extra credit by adding semantics not in the schema: videoIds should come from list_posts and omitting it yields the 20 newest videos. It does not elaborate on startDate/endDate beyond what the schema already documents.

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 ('Return views, watch time, average view duration... likes, comments, shares and subscribers gained for up to 50 YouTube videos') and defines the window scope. It is clearly separable from get_youtube_channel_insights by the per-video framing, though the description never names that sibling explicitly, so it falls just short of 5.

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 one actionable usage rule: 'omit it [videoIds] for the 20 newest', and points at list_posts as the source of ids. However it offers no guidance on when to choose this over get_youtube_channel_insights, get_instagram_insights, or other analytics siblings, and no prerequisites for accountId/profileId selection.

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