currencies_listGet the list of ECB reference currencies with their euro rates and decimal places, defining which conversions are possible.
Every currency in the ECB daily reference set, with its rate against the euro and the number of decimal places it is rounded to. Anything not on this list cannot be converted here.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v0.20.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly discloses the data source (ECB daily reference set), the fields returned (rate against euro and decimal places), and the scope limitation. While it does not state return formatting or ordering, it provides solid transparency for a simple read-only listing tool.
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 compact: two sentences that front-load the core purpose and then add the important constraint about unsupported currencies. Every sentence earns its place and there is no redundant or filler wording.
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 listing tool with no output schema, the description gives enough information about the result contents and scope to be usable. A minor gap is that it does not mention how to request specific data or how results are ordered, but those are not critical for this simple 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 tool has zero parameters, so the baseline is 4. The description appropriately focuses on what the tool returns rather than parameter details, since there are none to document.
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 that this tool returns every currency in the ECB daily reference set along with its euro rate and decimal places. It also establishes a clear boundary by noting that anything not on the list cannot be converted, which differentiates it from sibling conversion 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 the tool should be used to check which currencies are supported for conversion, especially through the sentence 'Anything not on this list cannot be converted here.' However, it does not explicitly say when to use this tool versus sibling tools like rates_latest, convert, or fx_rates_for.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.