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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond the schema by explaining that omitting the optional `service` parameter switches the result from a single price to a full price list. It does not mention currency, price freshness, or whether prices are guaranteed at order time.

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 waste, with the core purpose front-loaded and the optional-parameter rule immediately after. Nothing needs to be re-read.

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 lookup with no output schema, the description covers what is priced, the unit (per OTP activation), and the list-vs-single behavior. The only gap is the shape of the returned price data (currency, additional fields), which an agent might want before formatting results.

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%, so the baseline is 3; the description earns above that by explaining the semantics of the optional `service` parameter's omission, which the schema only marks as non-required without saying what happens. It adds no interpretation of the `country` pool values, but those are richly documented in 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 and resource with a precise unit: the retail price per OTP activation, for a service in a country. This is clearly distinguishable from inventory/balance siblings in substance, though it never names an alternative tool explicitly.

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 one concrete usage rule — omit `service` to list all services — which is genuine when-to-do-what guidance. It offers no guidance on when to call this instead of get_inventory or get_rental_offers, so the cross-tool routing 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.