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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, and the description largely restates those ('side effects: none', 'deterministic'), which earns no extra credit. What it does add beyond annotations is concrete operational limits – 64 KB JSON input, 1 s per call, 1 MB result – which are genuinely useful for deciding when and how to call 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 Spanish block is tight and front-loaded (purpose, when, not-for, effects, limits), but the definition is then duplicated in a partially truncated English block that ends with a dangling pointer '[EN completo / full EN: inputSchema.description]'. Roughly half the text is redundant translation rather than additional signal.

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 deterministic, four-parameter calculator, the description covers purpose, applicability, the competing sibling, side effects, determinism and input/output limits, and an output schema exists so return values need not be explained. Nothing an agent needs in order to call it correctly is missing.

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 baseline is 3, but the description adds real meaning by explaining the relationship between exempt_account and already_withdrawn_this_month (the exemption is a monthly 350 UVT cap per designated account) and by anchoring year to UVT. It does not, however, spell out how the exemption is prorated or applied against the current amount.

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+resource with exact semantics: computes Colombia's GMF (4x1000) of 0.4% on a withdrawal or transfer, with an optional 350 UVT monthly exemption for one designated account. It also names the sibling it is not (co-iva), so an agent can separate the two tax tools 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?

Explicit 'Cuándo/When' section gives the triggering condition (applying a Colombian DIAN/Ley Emiliani/COP/GMF/UVT rule exactly, e.g. invoicing or payment flows) and a 'No para/Not for' exclusion that routes IVA work to co-iva by name. This is the strongest pattern for tool selection.

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