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

With no annotations provided, the description carries the full burden. It discloses the rate source (commercial exchange rate of the day from the Central Bank) and the additional cost components (IOF and typical spread), which is substantial behavioral context. It does not explicitly state it is read-only, but that is implied by its nature as a converter.

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 concise sentences. The first sentence states the action and key behavioral details, and the second clarifies mandatory parameters and naming. There is zero redundancy or filler, and the most important information is front-loaded.

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 calculation tool with no output schema, the description adequately explains what it does and what it returns (the cost breakdown). It covers the core functionality and the rate source. It does not detail the exact return structure, but that is likely self-evident for a converter. The missing edge-case handling is minor.

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% and all three parameters have descriptions, so the baseline is 3. The description adds value by explicitly stating the parameters are mandatory and that names must be used exactly in English, which is not in the schema and prevents naming errors. This goes beyond the schema.

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 ('Converte') and resource (real, dollar, euro) and adds unique value by explaining it also shows the real international-card cost including IOF and spread. This clearly distinguishes it from simple currency converters and many calculate_* siblings that lack this added cost analysis.

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 implies when to use this tool (when conversion with international-card cost is needed) but does not explicitly mention alternatives or exclusions. It does not say 'use this instead of get_current_rates' or similar. The guidance is adequate but not explicit about when not to use it.

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