lookup_codice_destinatario

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

With no annotations provided, the description carries the full burden, and it discloses the important behavioral boundary: 'This tool performs format validation only, no live query against the SDI SOAP directory service or the IPA registry.' It also describes the per-channel cap as 'reference only, not enforced here', which prevents agents from assuming channel-wide allocation behavior. Success/error return shapes are documented too.

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 long but front-loaded with the core purpose and well-structured into paragraphs and a bulleted routing section. Every part adds context, though the per-channel cap detail is arguably tangential to validating a single code and could be trimmed or moved to a reference note without losing essential guidance.

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 when to call it, what parameters to provide, the of flags, expected return values on success and error, and two important exceptions ('0000000' routing and PEC-only). An output schema exists, so full return-field enumeration is unnecessary; the description is complete enough for an agent to select and invoke correctly.

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?

The input schema already has 100% coverage of both parameters, so the baseline is 3. The description adds valuable semantics by explaining the exact routing implications of 6-character, 7-character, and 7-zero codes, plus the PEC-only case. It also makes explicit the non-obvious 'at least one required' constraint despite no required parameters in the schema.

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 starts with a specific verb and resource: 'Validate the format of a CodiceDestinatario (SDI recipient code) or PEC address.' It goes on to specify the routing outcomes (SDI_CODE vs PEC) and clearly separates this tool from sibling validation or XML-building tools by tying it to build_transmission_header(). This makes the tool's purpose unambiguous and distinct.

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 says 'Call this before build_transmission_header()' and covers the 'at least one of codice or pec must be provided' requirement. It also clarifies the tool does format validation only and does not perform live lookups, but it does not explicitly compare against sibling validation tools such as validate_cessionario or validate_partita_iva.

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