Fetch real-time currency exchange rates between two currencies with bid/ask prices and conversion rates.
| Name | Required | Description | Default |
|---|---|---|---|
| to_currency | Yes | Target currency code (e.g., 'USD', 'EUR', 'JPY') to convert to | |
| from_currency | Yes | Source currency code (e.g., 'USD', 'EUR', 'GBP') to convert from |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must carry the behavioral burden. It adds useful context such as 'real-time' and return contents, but omits any mention of rate limits, data source, authentication, or error behavior.
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?
A single clear sentence with the key information front-loaded and no wasted words. It is appropriately sized for a simple fetch tool.
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?
The description covers the core function and return values (bid/ask, conversion rates), and the schema covers parameters. With no output schema, some behavioral details like error cases or rate limits are missing, but the tool is simple enough that this is largely adequate.
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 coverage is 100%, so the schema already documents both required parameters with examples. The description adds no parameter-level detail beyond what the schema provides, which is the expected baseline.
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 states a specific verb and resource: fetching real-time exchange rates between two currencies. It also lists return content (bid/ask, conversion rates), though it does not explicitly contrast with sibling 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?
Usage is implied by 'between two currencies', but there is no explicit guidance on when to use this versus alternatives or any prerequisites. For a simple lookup tool this is minimally adequate.
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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