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

Annotations only provide readOnlyHint/openWorldHint safety signals, and the description adds substantive operational context beyond them: the default window falls back three days because YouTube Analytics lags two to three days, and the call requires an analytics-granted connection. These are the freshness and authorization traits an agent needs before calling.

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 return payload, then defaults/lag, then the permission prerequisite, with no filler sentences. The metric enumeration is long but each item is genuinely returned data, so it earns its place. Slightly dense, but appropriately sized.

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?

There is no output schema, so the description must carry the return contract, and it does: it lists the metrics, top 10 videos, and audience breakdowns. Combined with the date defaults, the lag caveat, and the analytics permission requirement, an agent has everything needed to call this correctly.

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 50%: accountId and profileId carry descriptions, while startDate/endDate rely solely on a regex pattern with no wording. The description compensates partly by establishing that the window is UTC and that omitting dates defaults to 28 days ending three days ago. It adds real meaning for the undocumented date parameters.

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 gives a specific verb (return) plus resource (a YouTube channel's analytics) and enumerates exactly which metrics come back, so the agent knows what a call yields. It distinguishes channel-level data from the sibling get_youtube_video_insights only implicitly through the word 'channel', never naming the alternative. Clear purpose, but no explicit sibling differentiation.

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 states the operative context: a UTC date window, a built-in default of 28 days ending three days ago, and the precondition that the connection must have granted analytics. It never names an alternative tool or a when-not-to-use condition, so no exclusions are provided. Clear usage context without routing guidance.

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