verifactu_qr_url

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

No annotations are provided, so the description carries the full burden, and it does disclose one concrete behavioral trait: the inputs are validated ('validando NIF, número de serie, fecha e importe'). However it says nothing about failure behavior when validation rejects an input, whether any network/registry call occurs, or auth requirements, leaving meaningful behavioral gaps.

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?

A single front-loaded sentence with the verb first and the resource immediately after; the regulatory citations are dense but arguably earn their place by anchoring the output to a legal standard. No filler or redundant sentences, though the clause structure is somewhat packed.

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 and no annotations, the description does identify the return value (a QR URL) and the validated inputs, which is the core an agent needs. The optional entorno and verifactu parameters, which materially change the generated URL, are left entirely to the schema, so it is not fully complete for a regulatory tool.

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 the schema already documents all six parameters including formats (DD-MM-AAAA, 9 chars, 60 chars) and defaults. The description merely restates the four validated parameters and adds no syntax or constraint detail beyond the schema, 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?

States a specific verb and resource: 'Genera la URL del código QR tributario de una factura española', grounded in named regulations (VeriFactu, RD 1007/2023, Orden HAC/1177/2024). An agent understands exactly what is produced. It does not explicitly differentiate itself from the sibling url_consulta_json, which is also a URL generator, so it stops short of a 5.

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 by the purpose — the agent can infer it is used when a VeriFactu QR URL is needed. There is no explicit when-to-use/when-not-to-use, no prerequisites, and no naming of the sibling url_consulta_json as the alternative, which is a real routing risk given both tools emit URLs.

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