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

With no annotations, the description carries the full burden, but for a zero-parameter read-only reference list the risk surface is small. It discloses the payload ('passports with ISO codes') which is the main behavioral fact; it does not state whether the list is static, cached, or whether it includes all nationalities or only supported ones (a meaningful distinction it raises but never resolves).

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?

A single short sentence with no filler, front-loaded with the resource. It is terse to the point of omitting a verb, but there is no wasted 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 zero-parameter, no-output-schema enumeration, the description covers what an agent needs to call it and what it returns. It could resolve the nationality-vs-passport naming mismatch and note whether results are exhaustive, but the gap is minor for a tool this simple.

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 the baseline is 4; there are no parameter semantics to clarify or omit. The description adds nothing here because nothing 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?

The description states the resource ('all supported passports with ISO codes') but omits the verb and does nothing to distinguish it from list_destinations or other sibling listing tools. An agent can infer it is a reference enumeration, but cannot tell from the text how it differs from list_destinations or nationality-related siblings.

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?

There is no when-to-use guidance, no stated relationship to siblings like visa_lookup or passport_power, and no conditions or exclusions. Usage is only weakly implied by the word 'supported'.

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