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

Annotations already mark the tool as read-only and idempotent. The description adds behavioral context by specifying the data scope (~40 currencies) and the presence of as-of timestamps and sources in the response, going beyond the annotation's safety profile.

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 a single 13-word sentence, front-loading the core purpose and key attributes (currency count, timestamp, source) without superfluous detail. Every word contributes meaning.

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 parameterless, read-only tool with no output schema, the description sufficiently conveys what the agent will receive: current USD rates for ~40 currencies with timestamp and source. This is complete for an agent to select and invoke correctly, especially with good annotations.

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 no parameters, and the input schema is empty with 100% coverage. With zero parameters, the description has no obligation to explain parameter semantics, so the baseline score of 4 applies.

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 tool returns current USD exchange rates for approximately 40 African currencies, including per-currency timestamp and source metadata. This specific scope differentiates it from sibling tools like get_african_policy_rates or get_african_yield_curve, which cover different financial instruments.

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 phrase 'Current USD rates' conveys a clear use case: obtaining up-to-date FX rates for African currencies. It implies an exclusion of historical data but does not explicitly name alternatives or when-not-to-use scenarios, placing it at clear context without explicit exclusions.

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