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

With no annotations, the description must fully convey behavior. It states the contents returned and implies an idempotent read via 'call it once,' but it does not explicitly confirm read-only semantics, output formatting, or data freshness. For a simple parameterless list, this is minimally sufficient but not comprehensive.

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 concise sentences: the first enumerates the exact content returned, the second provides a clear usage recommendation. There is no filler, redundancy, or unnecessary detail.

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 no-parameter list tool without an output schema, the description adequately specifies what data will be returned and when to invoke it. Minor omissions like ordering, count, or update cadence are not critical for the stated purpose.

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 has zero parameters, so the schema imposes no burden. The description adds meaningful context about what the tool returns, which aligns with the baseline of 4 for parameterless tools.

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 identifies the tool as returning the list of covered countries with postal-code format, hierarchy labels, key facts, and time zones. The resource and scope are evident, though the lack of an explicit verb like 'lists' makes it slightly less direct. It does not strictly contrast with sibling tools, but the country-coverage focus makes its purpose distinct.

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 instruction 'Call it once if unsure whether a country is covered' gives an explicit condition for use and implies this is the go-to tool for coverage checks. It does not mention alternatives or exclusions, but the guidance is clear enough for routing an agent.

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