Currencies the ECB quotes

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

With no annotations, the description carries the full burden and does disclose key behavior: the list is exhaustive and authoritative, and contains rates and decimal places. However, it does not mention freshness, ordering, or whether the rates are live or static.

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 sentences deliver the full purpose and domain scope without redundancy. The key constraint is placed in the second sentence, making the description easy to parse.

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 list tool, the description is complete: it defines the contents, the authoritative scope, and the practical consequence of a missing code. No output schema is present, but the listed fields are enough for an agent to understand the result.

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 zero parameters, so the baseline of 4 applies. The description adds meaningful context about what each listed item contains, compensating for the lack of schema 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 tool exposes every currency in the ECB daily set, including its euro rate and decimal places. It also frames the resource as the authoritative domain list, distinguishing it from conversion and history tools.

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 it: to validate whether a currency code is supported before attempting conversion, quoting, or history retrieval. It does not explicitly name sibling alternatives, but the domain boundary is clearly communicated.

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