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

Annotations already declare read-only, idempotent, open-world, and non-destructive behavior. The description restates ordering and scope but adds little behavioral context beyond the schema, such as rate limits, caching, or output format (output schema exists).

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?

Front-loads the core ranking action and order behavior, but repeats 'order=most_expensive' and 'region or worldwide' across clauses, adding mild redundancy. Still compact and readable.

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?

Covers purpose, usage context, and ordering. With a rich schema, output schema, and annotations handling safety and returns, the definition is nearly complete for an agent; it omits only a note on locale/language effect, which the schema covers.

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%, so all five parameters are fully documented in the schema. The description only restates the order and region parameters without adding syntax, defaults, or usage nuance beyond the schema.

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 ('Rank countries') and resource (fuel price by region), with the ordering behavior. It is clear what the tool does, though it does not explicitly differentiate itself from siblings like compare_fuel_prices or get_fuel_prices.

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?

Provides clear context: useful for route planning and for answering 'where is fuel cheapest/most expensive' in a region or worldwide. It does not mention when not to use it or name alternative tools, so it stops short of a 5.

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