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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds value beyond them by disclosing the shape of each result entry and explaining the breakpoint flag's meaning ("higher precision at the tails") — the only real gap is what to do if a country is absent.

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 filler, with the resource and payload front-loaded and the call-to-action second. Nothing would be lost by trimming and nothing is missing that belongs here.

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 zero-parameter discovery tool with no output schema, the description supplies what the agent actually needs: the resource, that a per-country precision flag comes back, and that the output feeds country-code arguments elsewhere. Its only undischarged burden is the exact return format, which is low-risk for a simple enumeration.

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 no parameters, so there is nothing for the description to disambiguate and the baseline applies. Nothing in the text adds or obscures parameter meaning.

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 every country KeepUp has wealth-distribution data for") plus the per-entry payload ("whether it has full survey breakpoints"). It reads clearly as the discovery/enumeration tool in contrast to the net-worth query siblings, though no sibling is named to make the boundary explicit.

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?

"Call this to discover valid country codes" gives a concrete triggering condition tied to the sibling tools that need a country code. There is no explicit when-not guidance or named alternative, but for a zero-param lookup the positive case is unambiguous.

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