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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description 'List currencies' adds no additional behavioral context such as data scope, return format, or safety nuances. Since it provides no value beyond the annotations, it scores 2.

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?

The description is exactly two words, 'List currencies.' For a zero-parameter listing tool, this is appropriately sized and front-loaded. There is no wasted wording, so it earns a 5.

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?

Given the low complexity, zero parameters, strong annotations, and presence of an output schema, the description is minimally complete. It could optionally mention what currencies are included (e.g., fiat, crypto) but does not need to for a simple list-all operation, so it scores 4.

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 has zero parameters, so the baseline is 4. The schema is empty with 100% coverage, and the description does not need to explain parameters. Thus, it fulfills the requirement adequately.

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 'List currencies' uses a specific verb and resource, clearly stating what the tool does. It does not explicitly differentiate from the sibling tool 'currency', though the plural form hints at a listing versus single-item lookup. This is clear but lacks explicit sibling differentiation, so it is a 4.

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 guidance on when to use this tool versus alternatives like 'currency'. The description only states the action without any context for selection, so it scores 2 for no guidance.

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