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

Annotations already declare readOnly, idempotent and open-world, so the safety profile is covered. The description adds genuinely non-obvious context: the tool only works on public videos, and it costs 1 credit, which is exactly the kind of cost/scope information annotations cannot convey.

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, no filler: the first front-loads what is returned, the second covers the derived metrics and the credit cost. Every clause earns its place.

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 return-value burden and does so thoroughly, plus it discloses the public-only constraint and credit cost. The one real gap is sibling differentiation against get_video_info/get_video_heatmap for an agent choosing between near-duplicate tools.

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?

There is a single parameter at 100% schema description coverage ('YouTube video ID or URL'), so the schema already carries the semantics. The description adds nothing about accepted input forms, so baseline 3 applies.

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+resource and enumerates the returned fields in detail (view/like/comment counts, publish time, description, keywords, hashtags, chapters, links, music, related videos), which is well beyond a tautology. However, it never distinguishes itself from the close sibling get_video_info, leaving the agent unsure which of the two 'video detail' tools to pick.

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 when-to-use guidance, no exclusion criteria, and no reference to an alternative tool. With a sibling named get_video_info sitting right beside it, this omission is material rather than cosmetic.

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