validate_rfc_mx

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

The description discloses the exact return format (valid, type, rfc or valid false, reason) and validation rules, adding significant context beyond the annotations (readOnlyHint, idempotentHint).

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?

Four sentences, no wasted words: first states purpose and background, second gives format details, third return type, fourth use cases. Ideal structure.

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?

Given a single required parameter, output schema, and comprehensive annotations, the description covers all needed context for correct tool selection and invocation.

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?

With 100% schema coverage, the baseline is 3, but the description adds detailed format rules (character composition, homoclave) and examples, enhancing understanding beyond the schema's example.

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 it validates a Mexican RFC, specifies formats for individuals (13 chars) and companies (12 chars), and distinguishes from sibling tools that validate other Latin American identifiers (e.g., validate_cbu_ar, validate_clabe_mx).

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?

Explicitly says 'Use when processing Mexican CFDI invoices, supplier registration, or any Mexican tax compliance workflow,' providing clear, actionable guidance without ambiguity.

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