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

Annotations already establish readOnlyHint and idempotentHint, so safety is covered. The description adds useful behavioral context absent from structured fields by describing what the response contains (country codes plus public home and events page references), which matters since no output schema exists.

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 sentence with no filler, front-loading the resource and then the payload details. Slightly dense phrasing but every clause carries information.

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 simple, parameterless reference tool with no output schema, the description covers what is returned (countries, codes, page URLs) so an agent knows what it gets back. It could be marginally stronger by stating when to prefer it over the event-listing siblings.

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 there is nothing for the description to clarify or compensate for. Baseline 4 applies for a parameterless 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 names a concrete resource (countries Events.Aero lists events in) and the payload content (codes plus public home/events pages), which is specific enough to distinguish it from the event-oriented siblings. It is clear but never explicitly contrasts itself with siblings like list-event-types or search-events.

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 hints at usage by noting the code is 'to pass to other tools,' which implies this is a lookup/reference tool used before other calls. There is no explicit when-to-use statement or exclusion versus alternatives, so usage is only implied.

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