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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered, and the description partially repeats that with 'sin red, sin estado guardado'. However it adds genuinely new operational context: determinism guarantee and hard limits (64 KB input, 1 s per call, 1 MB result) that annotations do not carry, which is real value beyond structured fields.

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?

Content is well front-loaded with labeled sections (Cuándo / No para / Efectos / Límites) that make scanning easy. It is somewhat long because it duplicates the whole body in Spanish and English, which costs a bit of conciseness 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?

An output schema exists, so return values need not be explained, and the description still covers purpose, routing, side effects, determinism and execution limits. Nothing an agent needs to invoke 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% and the enum plus an example are already in the schema, so the schema does the heavy lifting. The description only mentions the general purpose of the two fields rather than adding format syntax or edge-case meaning, matching the baseline of 3.

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 (analiza/parses) plus the resource (phone number) and enumerates the exact country scope (CO, MX, BR, AR, CL, PE, EC, US, ES) and the outputs produced (country, type, E.164, national/international formats). It also names the sibling it is not (phone-e164-validate), so an agent can distinguish it 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:' clause tells the agent when to use it (offline verification of format and check digit before use) and the 'No para:' clause names the alternative tool for normalization (phone-e164-validate). This is explicit when/when-not/alternative guidance.

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