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

Annotations already declare readOnly, idempotent, closed-world, non-destructive, so the safety profile is covered. The description adds genuinely useful context beyond that: prices are monthly equivalents, yearly billing also returns the full-year total, and each response reports when prices and FX rates were last updated.

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?

Three sentences, front-loaded with the core action, then usage examples, then output caveats. No filler and nothing repeated from the schema verbatim.

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?

Output schema exists, so return structure need not be spelled out, and the description still flags freshness metadata. For an 11-parameter tool the description is adequate, though it says nothing about pagination or how an omitted plan resolves to the product's main plan beyond the schema note.

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 91%, so the schema already documents nearly every parameter including plan keys, sort order, currency defaults and channel behavior. The description only reinforces the 'converted to one currency' framing and does not clarify defaults or interactions beyond the schema, so baseline 3 applies.

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 and resource ('Rank the price of one subscription plan across countries and regions, converted to one currency') with concrete product examples. An agent can tell this is a cross-region price ranking, though the description never names or distinguishes itself from the close sibling get_region_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?

The example questions ('where is ChatGPT Plus cheapest?', 'how much is Claude Pro in Turkey?') map cleanly onto when to invoke this tool. There is no explicit exclusion or pointer to alternatives such as get_region_prices or compare_credits, so routing for ambiguous cases is left to inference.

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