Convert an amount

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

With no annotations provided, the description carries the full burden, and it delivers: it discloses the converted amount, the cross rate to 6 decimals, the rounding applied, and the rate date used. The parameter descriptions further reveal important behaviors like default-to-currency, minor-unit rounding, weekend/holiday fallback, and the 90-day window fallback. This gives an agent a reliable picture of the tool's behavior, including edge cases.

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 two tightly written sentences: the first front-loads the call action and scope, the second compactly enumerates the return contract. Every clause adds value, and the parameter descriptions are detailed without being bloated.

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?

There is no output schema, but the description compensates by listing the returned fields: converted amount, cross rate to 6 decimals, rounding applied, and rate date used. Combined with complete parameter documentation and fallback behaviors, an agent has enough information to invoke the tool correctly and interpret the result.

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 input schema has 100% coverage, with rich descriptions for all four parameters including defaults, rounding behavior, date fallback, and the euro cross-rate path. The main description adds high-level context but does not need to restate parameter details; the schema already does the heavy lifting.

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 operation ('convert an amount') with a clear resource scope: any two ECB-quoted currencies, today or on a past date. It is easily distinguished from sibling tools like convert_time or currency-rate lookups because it focuses on a single conversion and its output contract. The title and description reinforce each other without ambiguity.

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 opening phrase 'Call this tool to convert an amount' gives a direct, actionable usage instruction, and the scope (single amount, ECB currencies, date choice) defines the context clearly. It does not explicitly name alternatives such as convert_many or fx_rates_for, so it stops short of a full 5, but the guidance is well implied.

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