REST Countries — Country Profile

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

Annotations declare readOnly, idempotent, etc., but the description adds that there is no API key required and no rate limit, which are important behavioral traits not captured in annotations. This adds value beyond the structured data.

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 sentences only, both front-loaded with key information: first sentence tells what the tool does, second explains arguments. No extraneous text. Every sentence earns its place.

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 read-only tool with two parameters and no output schema, the description is almost complete. It explains input well and mentions the output fields. It could perhaps mention that the output is a rich JSON or markdown object, but the list of fields implies the structure. Overall, it's sufficiently complete.

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?

With 0% schema description coverage, the description adds significant value by explaining the 'country' parameter accepts names, ISO alpha-2, or alpha-3 codes with examples. The 'response_format' is clear from its enum and default. This compensates for the schema gap.

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 states the tool returns a full country profile listing specific fields (capital, region, etc.). The name and title also help. It distinguishes from siblings like globalpulse_countries_get_by_region which is a different operation.

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 description provides some usage context like 'No API key, no rate limit', but does not explicitly state when to use this tool over alternatives. The implied usage is for fetching a detailed profile of a single country, but no exclusionary guidance is given.

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