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

No annotations are provided, so the description carries the burden. The description says it identifies validity, carrier, and formatted forms but doesn't explain what happens with invalid numbers, edge cases, or any formatting behavior. It doesn't contradict annotations because there are none, but it lacks depth on behavior.

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 concise, two sentences, and front-loads the key information. However, it could be slightly more structured, but it's efficient overall.

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 does not explain return values or formats. The tool is relatively simple, but the description leaves out important details like how carrier is returned, what 'formatted forms' means, and how to handle invalid inputs. This is incomplete for an agent to use it effectively.

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%, and there are two parameters: 'phone' and 'number'. The description mentions 'phone = 11-digit number' but doesn't clarify the purpose of 'number' versus 'phone', nor whether both are required or how they differ. This is a significant gap, as the description does not compensate for the poor schema documentation.

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 states the tool identifies Chinese mainland phone numbers, carrier, and formatted forms. This clearly distinguishes it from siblings like pinyin_convert or id_card_check.

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 mentions the input is an 11-digit number, giving minimal context on when to use it. It doesn't explicitly state when not to use it or mention alternatives like china_reachability, but given the sibling list, the purpose is fairly specific.

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