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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so safety and idempotency are covered. The description adds genuine value beyond that by explaining the index semantics (world average = 100, higher = more expensive), which is interpretation an agent needs and cannot get from the structured 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?

Two compact sentences: the first establishes purpose and scale, the second establishes the usage trigger. Nothing is redundant and the most important framing (the index scale) is front-loaded.

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 an output schema present, annotations covering the safety profile, and full schema documentation, the description only needs to add interpretation and routing. It handles the index semantics and a usage trigger well, though it stops short of distinguishing this tool from its food-related siblings.

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 coverage is 100%, with both 'from'/'to' ISO codes and the 'locale' enum fully documented (including the fallback behavior when locale is omitted). The description adds no parameter-level detail beyond the schema, so the baseline 3 is appropriate.

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 (compare) and resource (food price index) and explains the scale so the agent knows what the number means. It does not differentiate itself from food-related siblings like get_country_food_prices, rank_food_prices, or the analogous compare_fuel_prices, leaving the agent to infer the distinction from the name alone.

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: 'when someone asks where food is cheaper between two countries.' This clearly sets context but names no alternatives or exclusions, so the agent must independently figure out when to prefer get_country_food_prices or rank_food_prices instead.

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