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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description adds useful behavioral context beyond that: the ranking criterion (MOST-WATCHED), the time window (last N days), and the exact output metrics. It does not cover auth needs, rate limits, or pagination.

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, front-loaded with the core purpose and returned fields, then a parenthetical note for the channel parameter. No filler and no wasted clauses.

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?

The tool is simple and annotations plus the output schema cover safety and return structure. However, with zero schema descriptions, the missing explanation of 'limit' and the absence of sibling routing guidance leave meaningful gaps for correct invocation.

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%, so the description carries full burden for three parameters. It explains days implicitly ('last N days') and channel explicitly, including its source and empty-default behavior, but omits 'limit' entirely, leaving one of three parameters with no meaning anywhere.

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 retrieval task (most-watched videos over last N days) and enumerates the returned metrics, so the agent knows what the tool produces. It references youtube_channels for channel names, which distinguishes that sibling, but does not differentiate itself from youtube_overview or youtube_traffic_sources.

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?

The only usage guidance is for the channel parameter ('leave empty if there is only one channel'). There is no guidance on when to use this tool versus other YouTube reporting siblings, and no exclusions or alternative conditions are given.

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