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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered; the description still adds genuinely new context in the form of determinism guarantees and hard limits (64 KB input, 1 s per call, 1 MB result). It loses a point because 'no network access, no stored state' largely restates the annotation set rather than adding to it.

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 labeled structure (When / Not for / Side effects / Deterministic / Limits) is good and front-loaded, but the content is duplicated wholesale in Spanish and English and ends with a dangling artifact ('[EN completo / full EN: inputSchema.description]'), roughly doubling length without adding information.

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?

With an output schema present, rich annotations and 100% schema coverage, the description needs only purpose, selection guidance and any behavioral caveats — all of which it supplies, including rate/size limits that an agent should know before calling.

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 all five parameters including the mode enum, currency pattern and fee percent bounds. The description only adds the conceptual frame (fee is percent + fixed, amount is the target net or the gross charge), which is essentially what amount's schema description says — baseline 3 applies.

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?

States a specific verb and resource — computing a processor fee (percent + fixed) to gross up a target net or derive the net from a gross charge — and names both directions explicitly. It also explicitly distinguishes itself from the closest sibling (discount-calculate), so an agent can route without opening either schema.

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?

Provides an explicit 'When' clause (money/tax/financial math that must be exact and reproducible) and an explicit 'Not for' clause naming the alternative tool (discount-calculate). The condition that selects this tool versus a discount calculator is stated, not inferred.

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