convert_currency

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

With no annotations, the description carries the full burden and does well: it discloses the data source (ECB via frankfurter.dev), the 1-hour cache, and the exact return keys. The inclusion of cost_usd hints at cost behavior, but it does not explain error handling or the meaning of that field, leaving a small gap.

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 efficiently structured: a one-sentence purpose, two short sentences about data source and caching, then Args and Returns sections. Every sentence adds necessary value, and the front-loaded purpose helps agents quickly understand what the tool does.

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 simple tool with no output schema or annotations, the description is largely complete: it covers the operation, all parameters, and the return structure. Minor omissions—undefined cost_usd, the overbroad 'any two currencies' claim, and no error scenarios—prevent a perfect score but do not block correct invocation.

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%, so the description fully compensates with an Args section that explains each parameter's meaning, provides ISO 4217 format guidance, and gives concrete examples for all three parameters. This is exactly what an agent needs to construct valid arguments.

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 opens with 'Convert an amount between any two currencies', a specific verb+resource statement that clearly identifies the function. Naming ISO 4217 currency codes and the distinction from sibling tools like convert_units and convert_timezone makes the tool's domain unmistakable.

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 gives clear context by stating the conversion scope and adding behavioral details about ECB rates and caching, which indicate when the tool is appropriate. However, it does not explicitly mention alternatives or when not to use it, though the sibling list makes those alternatives discoverable.

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