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

Beyond the readOnly/openWorld annotations, the description discloses result cap (up to 20), ordering (most-liked first), and the payment model ($0.002 USDC per successful call via x402, failed calls free). The billing and failure-charge behavior is exactly the kind of context an agent needs before invoking a paid tool.

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, no filler, purpose first then requirement then cost. Slightly dense as a single block, but every sentence carries distinct information.

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?

For a single-parameter read with an output schema and readOnly annotations, the description covers input format, result size/ordering, and payment terms. Nothing needed to call it correctly is missing.

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 coverage is 100%, so baseline is 3. The description adds meaning the schema doesn't carry: aid must be numeric, comes from the av-style URL, and BV ids are not accepted — this prevents a common wrong-input failure.

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 verb and resource ('Hot comments on one Bilibili video from Bilibili's public comment endpoint') and enumerates the returned fields, which distinguishes it from the other platform comment tools (facebook/tiktok/youtube_comments) without ambiguity.

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?

Gives a clear prerequisite (numeric aid from the av<aid> URL) and an explicit negative constraint: it does not convert BV ids. It lacks an explicit routing statement to sibling comment tools, but the platform scope is self-selecting.

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