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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful context by explaining that signed-in calls return the account's rate as account_rate true and anonymous calls return list_price true, though it does not describe error behavior or response shape beyond those flags.

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?

The description is three tight sentences, front-loaded with the core return value and followed by the signed-in distinction and the non-call-placement clarification. Every sentence adds useful information without repetition.

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 no output schema, the description usefully explains the returned rate semantics via account_rate and list_price. The main remaining gap is that all four parameters are optional and the description does not clarify what happens when neither destination nor country is supplied, or when number_type should be used.

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 only 50%: currency and destination are documented in the schema, while country and number_type are not. The description partially compensates by saying the tool prices a destination number or country, but it gives no guidance on number_type or on how the parameters interact when all are optional.

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?

The description states a specific verb and resource: it returns the per-minute price for dialling a destination number or country. It also explicitly distinguishes the tool from call placement with “This does not place the call,” so an agent can tell it apart from request_call or create_call_task.

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 signed-in versus not-signed-in behavior is clearly explained, but there is no explicit when-to-use guidance or named alternatives such as quote_call_task or get_did_rate. Usage is implied by the rate-checking context rather than stated as a decision rule.

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