Compare videos fairly

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

The annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is fully covered. The description adds one genuinely useful behavioral detail beyond that: comparisons are aligned by age since publishing rather than by calendar window, so short-lived videos are not penalized. It stops short of disclosing result shape, limits (max 5 IDs, single channel), or what happens when a video is newer than first_days.

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?

One sentence, front-loaded with the resource and the fairness/normalization rule, with zero filler. Nothing in it is redundant with the annotations or schema.

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?

An output schema exists, so return values need not be explained. However, for a comparison tool spanning 2-5 videos across multiple possible channels, the definition never says what dimensions are compared or that all IDs must belong to one channel, leaving the agent to infer scope from the schema.

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%, so the schema already documents all three parameters, including first_days and the UC... channel ID format. The description reinforces the meaning of first_days ('its own first N days') but adds nothing for video_ids or channel_id; baseline 3 applies when the schema does the heavy lifting.

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 verb and resource (compare videos) and states the core mechanic: each video is measured over its own first N days after publishing. It does not say which metrics are compared or how it differs from the neighboring youtube_get_video_analytics, so sibling differentiation is left to the name alone.

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?

There is no explicit statement of when to use this tool versus youtube_get_video_analytics or youtube_get_channel_analytics, and no prerequisites or exclusions. Usage is only inferable from the word 'Compare' and the phrase 'on equal footing', which suggests normalizing across videos of different ages but never says so directly.

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