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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds the endpoint mapping (GET /fax/send/prices) and the shape of the returned records, which is useful context, but says nothing about auth requirements, rate limits, or the fact that pricing may be extensive per country.

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 short sentences: the first front-loads what is returned, the second gives the API route. No redundancy or filler, and every clause carries information.

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 names the four returned fields, so an agent knows what to expect from an otherwise schema-less call. It is nearly complete for a trivial read-only endpoint; only auth/pagination notes are missing.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; per the rubric a 0-parameter tool baselines at 4. The description correctly implies no filtering input is required.

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 ('List the price of sending a fax per destination country') and enumerates the returned fields (country code, calling prefix, price, currency). It does not differentiate itself from the sibling notifyre_list_sms_prices, but the resource is unambiguous.

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 intent (retrieve fax pricing) is implied by the description, but there is no explicit when-to-use guidance, no mention of prerequisites, and no pointer to the near-identical sibling notifyre_list_sms_prices for an agent choosing between pricing endpoints.

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