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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description still adds real value beyond them: no network access, no stored state, determinism guarantee, and concrete limits (64 KB input, 1 s per call, 1 MB result). It does not describe the output shape, but an output schema exists.

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?

Front-loaded with the core action, then labeled sections (When / Not for / Side effects / Deterministic / Limits) that are easy to scan. The full Spanish/English duplication roughly doubles length, which is a cost, but no individual sentence is filler.

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 4-parameter, read-only calculation tool with full schema coverage, rich annotations and an output schema, nothing an agent needs to invoke it correctly is missing. Limits, determinism and the sibling exclusion are all present.

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 baseline is 3. The description nonetheless adds meaning the schema does not: rounding to the currency's minor units ties the currency parameter to observable behavior, and 'adds tax to a net amount or extracts it from a gross (tax-inclusive) amount' explains what amount_includes_tax actually toggles.

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 pair (adds/extracts) and resource (tax/VAT at any rate) plus the rounding behavior to minor units. It explicitly names the sibling it is not (co-iva) and why, so an agent can distinguish it without opening the 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:' condition (exact, reproducible money/tax/financial math) and an explicit 'Not for:' exclusion routing to co-iva for Colombian IVA at 19%/5%/0%. Both the positive and negative selection criteria are spelled out.

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