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

Annotations already declare read-only, idempotent, non-destructive behavior; the description adds meaningful scope details: exactly what country facets are returned, the split between curated and GeoNames entries, and the instruction to call it once. This goes beyond the annotation safety profile and clarifies the tool's output content.

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 tightly packed sentences lead with 'Coverage overview' and enumerate the specific data categories without filler. Every phrase adds useful information, and the use-case guidance is included without bloating the text.

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 parameterless read-only tool with no output schema, the description is complete: it tells the agent what data will be returned, names the data source, and explains when to invoke it. Nothing needed for correct invocation is 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 input schema has zero parameters)Skip, so no parameter documentation is needed. The description correctly implies that calling requires no arguments and focuses on the return content instead. This meets the baseline for a no-parameter tool.

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 clearly states the tool is a coverage overview of countries, enumerating the eight curated countries' data fields and the bulk_tier of ~115 additional GeoNames countries. This distinguishes it from the sibling lookup/search tools by targeting coverage checking rather than postal-code or region operations.

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?

It explicitly says to call the tool 'once if unsure whether a country is covered,' which gives a clear when-to-use condition. It does not name nearby alternatives or state when not to use it, but the coverage-checking purpose is sufficiently distinct from the sibling tools.

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