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

With no annotations, the description carries the transparency burden. It discloses that data is 'daily', covers '100+ currencies', and is sourced from US Treasury Fiscal Data, described as 'free, unrestricted'. This gives useful behavioral context without overpromising.

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 two sentences, front-loaded with the main verb and resource, and provides essential source information without fluff. Every word contributes value.

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 no output schema and no parameters, the description adequately explains the tool's output ('daily official FX rates for 100+ currencies') and source. It lacks some detail on output format (e.g., base currency, date handling) but is sufficient for a simple read-only retrieval tool.

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 input schema has zero parameters, so description can't add parameter details. However, it adds context about what the returned rates cover (official US Treasury rates for many currencies). Given the schema already shows no parameters, the description adequately complements it.

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's purpose: 'Get official US Treasury reporting rates of exchange' with scope 'daily official FX rates for 100+ currencies.' It uses a specific verb and resource, and the mention of 'US Treasury' distinguishes it from general FX tools like fx_get_rates.

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 provides clear context: use this tool when you need official US Treasury FX rates, specifically daily rates for 100+ currencies. It implies a distinct use case from sibling FX tools but does not explicitly name alternatives or exclusions.

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