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

Annotations already signal readOnlyHint=true; the description adds key behavioral traits: determinism, non-stamping, non-substitution of PAC, and informative nature. No contradiction with annotations.

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 sentences, front-loaded with the core action and scope, followed by important caveats. Every sentence provides value without redundancy.

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?

The description covers purpose, usage, and behavioral traits well, but lacks information about the return value or output format. Since no output schema exists, the agent would benefit from knowing whether the tool returns a boolean, error messages, or details. This omission reduces completeness.

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 baseline is 3. The description summarizes the parameter relationship ('relacion entre tipo...') but does not add significant detail beyond the schema descriptions. The term 'coherencia' provides context but not per-parameter clarification.

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 clearly states the verb 'Valida' and the resource 'CFDI 4.0', and specifies the validation scope: 'relacion entre tipo de comprobante, uso, metodo/forma de pago y tipo de receptor, contra los catalogos del SAT'. It distinguishes from siblings by mentioning determinism and what it does not do (timbra, sustituye PAC).

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?

The description explicitly states when to use ('antes de emitirlo') and what not to do ('NO timbra ni sustituye al PAC', 'Informativo, no asesoria fiscal'). It does not explicitly name alternative tools but provides enough context for appropriate usage.

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