country_by_region

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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds only the upstream source ('REST Countries') and nothing about result volume, whether all countries in a region are returned, or error behavior for an unrecognized region.

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?

One sentence with no padding, front-loaded with the verb and resource. It is efficient but borders on under-specification given the undocumented parameter.

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 lookup tool with zero schema coverage and no output schema, the definition should at minimum enumerate valid region values and sketch the returned country shape. Neither is present, leaving the agent guessing at the one input it must supply.

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?

Schema description coverage is 0% for the single required parameter, so the description carries the full burden—but it only repeats 'region' without listing valid values (continent names? subregions? codes?) or case conventions. An agent could easily pass an invalid value such as 'EU' instead of 'Europe'.

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 ('Get') and resource ('countries') with a scope qualifier ('by region'), which distinguishes it from country_all and country_by_name. It does not explicitly name those siblings, so an agent must infer the routing.

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 statement of when to use this versus country_all, country_by_name, country_by_code, or country_by_currency, and no mention of what 'region' means or which alternatives exist. Usage must be inferred from the tool name alone.

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