country_by_currency

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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior. The description adds only the upstream source ('REST Countries') and does not describe matching behavior, case sensitivity, or whether multiple currencies are supported.

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 with no filler. It is efficient, though it is arguably too terse for the missing input-format detail.

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 one-parameter lookup with annotations covering safety and no output schema, this is close to adequate. The missing currency-code format is the main incompleteness, since an agent could pass a country name or currency name and get an error or unexpected result.

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%, so the description must carry the parameter semantics. It says 'by currency' but never specifies that the value should be an ISO 4217 currency code (e.g. USD), nor whether case matters — a meaningful gap for a single required parameter.

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 a clear verb and resource: get countries filtered by currency. The 'by currency' qualifier distinguishes it functionally from siblings like country_by_code or country_by_region, though it does not explicitly name an alternative.

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 filtering basis implies when to use it (when a currency is known), but there is no explicit guidance on when to prefer country_by_code, country_by_name, or country_info_detail. Usage is inferable but not directed.

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