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

With no annotations, the description carries the full burden and does well: it discloses the cost (1 crédito), the internal check performed (dígito verificador), and what the response contains. The notable gap is undefined failure semantics — it never says whether an invalid CUIT raises an error or returns a negative result, which materially affects how the agent handles the call.

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?

One dense sentence that front-loads the core action, then the accepted format, then the returned fields, then cost. Nothing is padding and nothing important is buried.

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 single-parameter, side-effect-free lookup with no output schema, the description covers input format, processing, return values, and cost — everything needed to invoke it correctly. Only the invalid-input behavior is left unstated, a minor but real omission given there are no annotations to fall back on.

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% for the single 'cuit' parameter, and its example already shows both the hyphenated and unhyphenated forms, so the schema does the heavy lifting. The description's '11 dígitos, con o sin guiones' largely restates that, adding no validation rules such as character restrictions beyond what minLength/maxLength already encode.

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 and resource ('Valida un CUIT o CUIL argentino') plus the exact scope (11 dígitos, con o sin guiones) and the output produced (dígito verificador, tipo, formato canónico). An agent can distinguish it from sibling validar_cbu, which handles a different identifier, 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?

The accepted input forms ('con o sin guiones') tell the agent the tool tolerates both raw and formatted IDs, which is practical invocation guidance. However, there is no explicit when-to-use/when-not statement or routing to alternatives (e.g. normalizar_telefono_ar for other normalization needs); usage is clear by implication rather than stated.

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