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

With readOnlyHint=true and openWorldHint=true already declared, the description adds real value: the data-lag behavior (two-to-three-day Analytics latency) and the authorization prerequisite (analytics scope must be granted on the connection). It does not describe failure behavior when the scope is missing or any rate-limit/throttling characteristics, so it is strong but not complete.

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?

Three tightly written sentences: return contents first, then default window and rationale, then the permission requirement. Every clause earns its place and the most decision-relevant information (what you get) is front-loaded.

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 and four parameters, the description carries the burden well by enumerating the returned metrics and demographics, stating the default time window and its cause, and flagging the analytics-grant prerequisite. An agent has enough to decide to call it and to predict the result shape.

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 only 50% – startDate and endDate have no schema descriptions – and the description compensates by defining them as a UTC date window with a stated default of 28 days ending three days ago. accountId and profileId semantics are covered by the schema itself. The description does not restate the YYYY-MM-DD format or the boundary inclusivity of the window, leaving minor gaps.

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 (Return) and resource (a YouTube channel's analytics), then enumerates the exact metrics returned: views, watch time, average view duration, subscribers gained/lost, likes, comments, shares, top 10 videos, and audience demographics. That scope ('channel' + daily metrics) cleanly separates it from the per-video sibling get_youtube_video_insights without needing the 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 clear operating context: the default window (28 days ending three days ago), why that default exists (Analytics lags two to three days), and the precondition that the connection must have granted analytics. It stops short of naming an alternative tool or stating when a caller should prefer video-level or other-platform insights, so it is context-rich but not exhaustively routing.

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