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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world behavior. The description adds 'Stores nothing', which usefully reinforces the no-side-effect nature, and it states the accepted numeric range. It does not need to repeat annotation-covered traits, so this is a solid addition.

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 short sentences with zero waste. The core purpose and example are front-loaded, and 'Stores nothing' is a compact, useful behavioral note.

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 one-parameter formatting tool with full annotations and an output schema, the description covers purpose, range, example, and side-effect profile. Minor gaps like behavior for out-of-range input are not critical because the range is stated and the tool is read-only.

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 100%, so the parameter itself is well documented. The description goes beyond the schema by supplying the accepted range (0 to 999.999.999,99) and a full input-to-output example, which clarifies accepted formats and expected output shape.

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 (writes) and resource (amount in Brazilian reais in words), with a concrete example and format. It does not explicitly differentiate from siblings, but the sibling tools are document-related and the purpose here is unmistakably a formatting utility, so the risk of confusion is low.

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 description: convert a monetary amount to its written form. There is no explicit when-to-use guidance, no mention of alternatives, and no exclusions. For a simple utility this is adequate, but it lacks the routing cues that would earn a higher score.

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