Convert an amount from one currency to another using indicative exchange rates from a free, no-key API.
Convert an amount between currencies using a free no-key rate API.
Rates are indicative, from exchangerate-api.com, and are not financial advice. Rates are cached in memory for 5 minutes.
| Name | Required | Description | Default |
|---|---|---|---|
| amount | Yes | ||
| to_currency | Yes | ||
| from_currency | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With zero annotation coverage the description carries the full behavioral burden, and it does disclose several useful traits beyond the schema: no API key required, upstream source exchangerate-api.com, indicative (non-authoritative) rates, a 'not financial advice' caveat, and a 5-minute in-memory cache. However, it omits what happens on an invalid or unsupported currency code, whether unsupported pairs are rejected or approximated, and whether any rate limiting applies to callers.
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?
Three short sentences with no filler, and the core action is front-loaded ahead of the provenance and caveat details. The mid-sentence line breaks are cosmetic noise but do not impair readability.
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?
An output schema exists, so return values needn't be explained, and the caching and disclaimer context is genuinely helpful for a rate lookup. What is missing for a three-required-parameter conversion tool with no schema descriptions is any specification of currency code format or amount constraints, which an agent needs to invoke it correctly on the first try.
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 0% and all three parameters are required with no titles beyond bare names, so the description is the only source of meaning. It says nothing about expected currency code format (ISO 4217 like 'USD' vs a name), casing, or whether amount may be negative or zero. It only indirectly implies the parameters by describing the operation.
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 gives a specific verb ('Convert') and resource ('an amount between currencies') plus the mechanism ('a free no-key rate API'), so the operation is unambiguous. No sibling tool deals with currency, so no explicit differentiation is needed or provided, which caps it just below the top mark.
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?
Usage is implied by the purpose rather than stated: there is no explicit 'use this when...' guidance, no mention of when a different tool would be preferable, and no prerequisites called out. Given the sibling set contains nothing adjacent to currency conversion, the omission is low-risk but still a gap.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.