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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the trailing 'Read-only' adds nothing beyond structured data. The one piece of genuine context is that returned codes are the exact values search_packages expects, which is useful interop information. No statement about whether the list is static or region-filtered, and 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 front-loaded sentence covering purpose, return shape, and downstream use. The trailing 'Read-only' sentence is redundant with the annotations and slightly dilutes an otherwise tight definition.

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 lookup with no output schema, the description covers what matters: it states the return fields and how they chain into search_packages. It could note whether the list can be narrowed (e.g., by region via get_regions) but nothing critical 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 tool takes zero parameters, so the baseline is 4. The description appropriately spends no words on parameter semantics and instead characterizes the return fields.

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 ('Lists') and resource ('destination countries'), and adds what each entry contains (names plus two-letter codes). It also ties the output to search_packages, which helps an agent place it in the workflow, though it doesn't explicitly differentiate itself from get_regions.

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?

Usage is implied rather than stated: the reference to 'the two-letter country codes used by search_packages' signals this is a prerequisite lookup for package search. There is no explicit guidance on when to prefer it over get_regions or search_inspirations, and no exclusions.

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