Convert an amount between ~50 currencies at the official reference rate (Bank Al-Maghrib for MAD pairs, ECB otherwise, cross via EUR), with rate, date and source. Price: $0.002 USDC per call, paid with x402 on Base.
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | ISO 4217 code | |
| from | Yes | ISO 4217 code | |
| amount | No | Positive amount, default 1 |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. It usefully discloses that the tool returns rate, date and source, and that calls cost $0.002 USDC via x402 on Base, but it does not explain payment prerequisites, error behavior, rate limits, or freshness guarantees beyond the source reference.
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 and front-loaded, stating the conversion purpose first and then the source and pricing details. Every sentence adds useful information without repetition.
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 paid FX conversion tool with no output schema, the description covers the rate sources, included output fields, and cost. It remains incomplete on payment mechanics for x402, possible conversion limitations, and failure modes, which matter for an agent invoking a paid endpoint.
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?
Schema description coverage is 100%, so the input schema already documents the three parameters, including ISO 4217 codes and the default amount of 1. The description adds no parameter-level detail beyond that, so the baseline of 3 is appropriate.
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 specifies a clear verb and resource: converting an amount between roughly 50 currencies using official reference rates. It adds useful scope details such as Bank Al-Maghrib for MAD pairs, ECB otherwise, and EUR cross-rates, but it does not explicitly differentiate this tool from sibling FX tools like macro_fx.
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 intended use is implied by 'Convert an amount between ~50 currencies,' and the rate-source context helps an agent understand the data basis. However, there is no explicit when-to-use guidance, no exclusions, and no named alternatives such as macro_fx for related FX data.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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