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

With no annotations, the description carries the disclosure burden. It usefully scopes the data to 'current' weather and implies a read-only comparison, but it does not mention failure behavior, units, or data source limitations. This is adequate for a simple query tool, with some gaps.

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?

A single sentence with no filler; the verb and target are front-loaded. Every part of the description contributes to understanding the tool.

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?

The tool is simple and an output schema exists, so return-value details need not be in the description. However, the definition lacks guidance on city-name formatting and does not explicitly contrast with get_weather, leaving minor but relevant gaps for an agent selecting the tool.

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 the description does not compensate by explaining how city names should be formatted or disambiguated (e.g., 'London, UK' vs 'London'). The names city_a and city_b are self-evident, but no additional meaning is added.

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 uses a specific verb ('Compare') and a clear resource ('current weather between two cities'), so an agent knows exactly what operation is offered. It does not explicitly name sibling tools, but the two-city scope distinguishes it from get_weather.

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 phrase 'between two cities' implies when the tool should be used, but the description does not explicitly say to prefer get_weather for a single city or mention any exclusions. Usage context is reasonably clear, but alternatives are left to inference.

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