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

Beyond the annotations (readOnly, idempotent, non-destructive, closed-world), it discloses that the full list is returned in one call (no pagination or paging loop), that it takes no parameters, and that it is a public tool requiring no sign-in and no billed API request. The auth and cost disclosure is exactly the extra context annotations cannot convey.

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?

Four short sentences, tightly front-loaded: purpose and return shape first, then routing guidance, then cost/auth note. Every clause carries information an agent would otherwise have to guess.

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?

There is no output schema, but the description covers the return shape, cardinality (full list in one call), and the absence of parameters, so nothing an agent needs to call it correctly is missing. The pre-call use case for downstream PPP tools is also spelled out.

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?

There are zero parameters, so there is nothing to disambiguate and the baseline applies. The description still usefully confirms "takes no parameters," but adds no further semantic depth because none is possible.

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 ("Return the supported countries and their official currencies") and even gives the exact return element shape `{ code, name, currencies }`. It explicitly distinguishes itself from `list_currencies`, so an agent can separate the two without opening either schema.

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 two concrete when-to-use cases (resolve a country name to an ISO alpha-3 code before `get_ppp_factor`/`analyze_ppp`, and check coverage) and names the sibling to use instead for currency codes. There are no parameters to qualify, so the guidance is complete rather than partial.

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