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

Annotations already indicate read-only, open-world, idempotent behavior. The description adds no additional behavioral context such as data source, return fields, or limitations, so it does not go beyond the structured annotations.

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?

It is very short but under-specified rather than concise; the two-word phrase does not earn its place because it communicates almost nothing about the tool's purpose.

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 tool, the description still lacks the core action and usage context needed to select and invoke it. The presence of an output schema helps, but the description leaves the agent guessing what the tool actually does.

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 schema has a single required currency_id with examples but no descriptions; the description does not explain parameter semantics or accepted values. With 0% schema coverage, this leaves the agent without any compensation.

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 'Single currency.' merely restates the tool name and lacks an actionable verb (e.g., 'get', 'fetch'). It provides minimal differentiation from the sibling 'currencies' tool only by implying singular scope.

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?

No guidance is given about when to use this tool versus 'currencies' or other product tools. There is no mention of use cases, exclusions, or context.

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