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

Annotations already declare this as read-only, idempotent, and non-destructive, but the description adds substantial behavioral context: it does not generate the telematic file (because it is not publicly reproducible), it never fills missing data silently (explicit errors), it validates VAT offline, and it is deterministic with no login required. This exceeds the baseline set by the annotations.

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 dense but front-loaded with the core purpose and validation scope, followed by important limitations, alternatives, and disclaimers. It is long, but for a complex tool with many validation rules, every sentence carries necessary information. It could be slightly more structured with bullet points, but it remains highly informative.

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 specifies exactly what the tool returns (populated sections, totals, deadline, control report), enumerates the validation rules and exclusions (e.g., XI only for goods, SM/GB rejected), and clearly states the major caveat about not generating the telematic file. Combined with the exhaustive input schema, the agent receives a complete operational picture even without an output schema.

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 has 100% description coverage with detailed explanations of every parameter, including enums, patterns, and cross-field constraints. The tool description adds only high-level guidance like using intrastat_periodicity first and does not provide any field-specific semantics beyond what the schema already offers, so it does not meaningfully enhance the schema's documentation.

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 the tool's function: composing and validating INTRASTAT sections from operation rows, assigning each row to the correct section, and returning populated sections, totals, and a control report. It distinguishes itself from sibling tools by explicitly naming intrastat_periodicity and verify_payee for related but different purposes.

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?

It explicitly instructs to determine periodicity first with intrastat_periodicity and to use verify_payee for live VIES, while this tool only validates offline. It also states that the tool does NOT generate the telematic file and that the official channel must be used, providing clear when-to-use and when-not-to-use guidance.

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