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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes beyond them with real operational context: values keep growing for days, YouTube data arrives 2-3 days late, and a paid plan with connected accounts is required. What it doesn't cover is the failure/latency path (e.g. what comes back for a video that isn't posted yet or an account without a connected network), so it falls just short of 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?

It is front-loaded with the resource and then the returned metric set, followed by the freshness caveat and the sibling routing sentence — no filler. The long metric enumeration is dense but each item carries information an agent may need to decide relevance, though the run-on paragraph form is slightly heavy.

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 takes on the burden of describing return values and does so by listing the metrics plus the fact that measurement timestamps are included, along with plan and freshness constraints. It is nearly complete; only the zero-data / not-yet-posted case is unaddressed.

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 0% for the single video_id parameter, so the description has to compensate. It implies the video must be 'posted' and refers to a single video, which narrows the expected identifier, but it never states the identifier format (internal ID vs. platform video ID) or whether unpublished videos are accepted.

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 states a specific verb+resource (the per-network metrics of one posted video) and enumerates exactly which numbers come back, so an agent knows what it gets without opening anything else. It also explicitly separates itself from the sibling get_stats, which returns account totals, so the two stats tools are distinguishable at a glance.

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?

It names the alternative ('For the totals of the account use get_stats') and the condition that selects it, plus the prerequisite 'Paid plans with connected accounts.' That is explicit guidance on both when to use this tool and when to use the other one instead.

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