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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the description does not need to repeat safety. It usefully adds that prices are 'current' and the output is sorted, but it does not disclose edge behavior such as handling invalid/missing country codes, price staleness, or exact response fields.

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 one concise, front-loaded sentence that states the action, scope, and return ordering. There is no redundant wording or repetition of schema details.

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 two-parameter, read-only tool, the combination of the description, full schema coverage, and annotations provides enough to invoke it correctly: fuel type, country codes, count bounds, and expected sorted output. It lacks explicit output field names, but no output schema exists and 'sorted table cheapest-first' gives a reasonable expectation.

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%, with fuel_type fully enumerated and defaulted and country_codes constrained to 2-10 ISO alpha-2 codes. The description reinforces the country-count and single-fuel-type scope but adds little semantic detail beyond what the schema already provides.

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 action ('Compare'), the resource ('current prices for one fuel type'), and the scope ('across 2-10 countries'). It also specifies the return behavior ('sorted table cheapest-first'), which distinguishes it from likely siblings like get_fuel_prices or find_cheapest_fuel.

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 the use case: comparing a single fuel type across a bounded set of countries and getting a sorted result. However, it does not explicitly say when to use this tool instead of siblings such as find_cheapest_fuel or get_fuel_prices, nor does it mention exclusions or conditions.

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