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

Annotations already declare readOnly, openWorld and idempotent, and the description goes well beyond them: failed calls are not charged, the tool is paid via x402 USDC on Base at $0.002 per successful call, and a payment-less call returns a PaymentRequired object. That is exactly the billing and failure behavior an agent needs before invoking a paid endpoint.

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?

Three sentences: use case first, accepted inputs second, payment model last. Every clause carries information (payload fields, input formats, price, error-charging policy) and nothing is repeated from the annotations.

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 compensates by enumerating the returned fields (views, duration, approximate publish date) and the volume cap, and it covers the paid-invocation flow. An agent has everything needed to call it correctly and interpret the result.

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 channel, limit and tab are already documented in the schema. The description restates the accepted channel identifier formats (@handle, URL, UC… ID) and the 50-item cap but adds no new syntax or semantics, so the 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 resource (a YouTube channel's published content) and the concrete payload returned: up to 50 latest videos, shorts or streams with views, duration and approximate publish date. This clearly separates it from siblings like youtube_video, youtube_playlist, youtube_search and youtube_comments without opening any schema.

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?

"Use when you need what a YouTube channel has published" gives an explicit triggering condition, and the tab enum is described as which feed to pull, implying the selection logic. It stops short of naming when to prefer a sibling (e.g. youtube_search for cross-channel queries), so no exclusions are stated.

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