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

Beyond the readOnlyHint annotation, the description discloses two facts the annotation cannot: the operation runs offline, and each call costs $0.002 USDC via x402. That payment requirement is exactly the kind of pre-invocation constraint an agent needs. It stops short of saying how an invalid CURP is reported (returned flag vs. error), which is the one remaining behavioral gap.

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?

Three short sentences, front-loaded with the verb and resource, then the decoded outputs, then the operational facts (offline, price). Nothing is wasted and no 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?

With no output schema, the description carries the burden of describing results, and it does so at a useful level: a validity determination plus decoded sex, birth date, and state of birth. The commercial and offline constraints are covered too; only the exact response shape and invalid-input behavior are left unspecified.

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% and the single parameter is already documented as "CURP to validate, 18 characters"; the description only restates the 18-character constraint. It adds no format, casing, or normalization guidance beyond what the schema provides, so the baseline 3 applies.

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?

Names a specific verb ("Validates") and resource ("Mexican CURP"), then enumerates exactly what is checked (18-character structure, check digit) and what is decoded (sex, birth date, state of birth). That is enough to separate it from similarly-shaped siblings like rfc_validar or sat_cfdi_verificar without opening their schemas.

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?

Usage is only implied: an agent can infer this is the tool for checking a CURP string, and "Offline" signals no network dependency. There is no explicit when-to-use/when-not guidance and no named alternative for adjacent identity/tax-ID validation tasks, so an agent must reason about routing on its own.

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