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

With no annotations provided, the description carries the full burden. It discloses the probe originates from a real China Mobile backbone node (not overseas inference), provides billing transparency ('self-validation failure not charged'), and indicates the output is a PDF report. This adds meaningful behavioral context beyond the minimal schema. However, it does not mention potential side effects, authorization needs, or concurrency limits, but for a read-only reporting tool this is adequate.

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?

The description is a single concise sentence that packs all essential information: what it does, how it works (source), parameter format, limit, and billing caveat. No wasted words, front-loaded with the main purpose, and perfectly structured for quick comprehension.

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?

Given the tool's moderate complexity (2 params, no output schema), the description covers the key aspects: purpose, input format, limits, test origin, output type, and billing condition. It lacks details on error handling or return format specifics, but since output schema is absent, mentioning 'PDF report' suffices. The description is sufficiently complete for an agent to invoke correctly.

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 must compensate. It explains the 'urls' parameter can be an array or comma-separated list and is limited to 20, but it does not mention the 'url' parameter at all. The description clarifies one parameter meaningfully but leaves the other undocumented, providing partial compensation.

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 clearly states the tool checks reachability of a batch of URLs from mainland China and generates a PDF report with per-URL conclusions, latency, HTTP status, and DNS-resolved IPs. It uses a specific verb ('reachability check') and resource ('batch of URLs') and distinguishes itself from the sibling 'china_reachability' by detailing the report format and testing source (China Mobile backbone).

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 description implies usage for checking mainland China accessibility, but does not explicitly say when to use this tool versus alternatives. It mentions input limits (max 20 URLs) and pricing conditions, but lacks explicit exclusion statements or references to sibling tools. The context is clear but not directive enough for an agent to choose it over similar tools.

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