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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety is covered; the description adds the index interpretation (100 = world average) and the consequential locale behavior (answer and interactive card language/units, fallback to app interface language). It omits tie-breaking or coverage caveats, but adds real context beyond the annotations.

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?

Two sentences, zero filler, with the ranking behavior and index scale front-loaded before the routing sentence. Every clause carries information an agent needs.

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?

A read-only listing tool with zero required parameters, documented defaults, three enums and an output schema that carries the return shape. Nothing needed for correct invocation is missing, and the locale caveat covers the one behavior the schema underplays.

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 enums and defaults documented for order, region, locale and limit, which sets the baseline at 3. The description restates the order semantics but adds no syntax or edge-case detail beyond what the schema already provides for any parameter.

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) and resource (countries by food price index), defines the index scale (world average = 100), and specifies the scope (region or worldwide). The 'use it when someone asks where food or groceries are cheapest' framing also implicitly separates it from sibling tools like compare_food_prices and get_country_food_prices, which answer different questions.

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?

Gives an explicit trigger condition: use when a user asks where food/groceries are cheapest or most expensive. That is clear context for invocation, but it never names the alternative siblings (compare_food_prices, get_country_food_prices) or states when those should be preferred, so there is no explicit exclusion.

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