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

With no annotations provided, the description carries the full burden. It accurately states that the tool returns a list of 31 currency codes and names. This is sufficient behavioral transparency for a read-only list operation, though it does not mention rate limits or authentication requirements.

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 exceptionally concise, using two sentences to convey purpose, scope, and examples. No wasted words; the key information is front-loaded in the first sentence.

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 tool's simplicity (0 parameters, no output schema, clear purpose), the description is complete. It explains what the tool does, the number of items, and examples. No additional information is necessary for correct usage.

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 no parameters (0 params, schema coverage 100%). The description adds no parameter information because none is needed. The baseline for 0 params is 4, and the description meets that expectation without adding unnecessary detail.

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 action ('list'), the resource ('currency codes and names'), and the scope ('all 31 available' with examples). It effectively distinguishes this tool from siblings like fx_convert or fx_get_rates by specifying that it provides the list of available currencies for foreign exchange queries.

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 implies when to use this tool: when you need the list of available currencies for foreign exchange queries. However, it does not explicitly state when not to use it or mention alternatives like fx_get_rates. The context is clear but lacks exclusionary guidance.

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