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

Annotations already declare the read-only, non-destructive safety profile, so the bar is lower; the description nonetheless adds real behavioral context beyond them — the list is configuration-driven and changes, implying results should not be cached or hard-coded. It omits nothing safety-critical.

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 tight sentences: the first defines the resource, the second carries the actionable directive. Nothing is redundant and the operational guidance is front-loaded.

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 zero-parameter, read-only enumeration call with no output schema, the description covers purpose and usage adequately. It could briefly note the return shape (e.g., a flat list of pair codes) to fully close the loop, but nothing essential is missing.

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 takes zero parameters, so per the rubric the baseline is 4. The description correctly implies a parameterless enumeration and introduces no parameter concepts that would need explanation.

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?

States a specific verb (List) and resource (currency pairs) scoped to Guard pricing, which separates it cleanly from pricing tools like price_guard or get_spot_rate. An agent can tell immediately that this is the configuration/enumeration tool, not a pricing call.

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 gives an explicit directive — always call this rather than assuming supported pairs — which is exactly the routing guidance an agent needs before calling any Guard pricing sibling. It does not name a specific alternative tool or state when-not to call it, keeping it just short of a 5.

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