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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds value beyond that by disclosing what the payload contains (per-level speed, rank, topic share) and that the channel must be in LingoDew's library, which is behaviorally relevant context an agent would otherwise have to guess.

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?

A single front-loaded sentence that leads with what is measured, then lists the metric set, then closes with the use case. No filler, no repetition of the title.

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 carries the burden of describing return content and does so thoroughly. What remains unclear is what 'level' means as a discrete value and what happens when a channel is not in the library — minor gaps for a two-parameter read-only tool.

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 100%, with both parameters documented and an enum for language, so the description need not explain them. The phrase 'per level' is not a parameter and adds no clarification about how channel identifiers are matched (name vs id vs URL). Baseline 3 is appropriate.

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 names a specific resource (a YouTube channel in LingoDew's library) and enumerates the exact metrics returned: video count, per-level speaking speed, rank, video share and main topics. This is clearly a stats-retrieval operation, distinct from find_videos and word_in_videos, without needing to name them.

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 a concrete use case: 'Useful for picking channels that suit a learner's level.' That gives clear context for when to reach for it, but there is no explicit when-not guidance or pointer to a sibling alternative.

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