VAT by filing period

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

Annotations already declare readOnly, idempotent, non-destructive, but the description adds substantive behavior: closed periods come from UOL's exact DPH closing document while open periods are estimates computed with stated rules (output VAT by DUZP, input VAT by later of DUZP and receipt date). It also discloses what is excluded (proformas skipped, corrective invoices as credit notes, internal documents and reverse charge omitted), which is exactly the accuracy caveat an agent needs.

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?

Front-loaded with the resource and returned values before the caveats, and each clause carries real information (estimation rules, exclusions). The second sentence is a long run-on with semicolons, but trimming it would lose material accuracy caveats.

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 read-only reporting tool with an output schema and fully documented parameters, the definition covers derivation, accuracy, ordering and exclusions well. It is slightly silent on scope (which company/workspace the figures belong to and how far back the periods extend), but that is minor given the surrounding sibling tools.

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 `periods` parameter already documents its 1-12 range and the 4/2 default per payer type. The description mentions monthly/quarterly periods only as a company-settings fact, not as parameter meaning, so it adds nothing beyond the schema — 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?

The description names the resource precisely (VAT/DPH per filing period) and enumerates the returned figures: output VAT, input VAT, amount to pay or excess deduction, due date, plus the sort order (newest first). No sibling tool covers VAT, so an agent can identify this tool from the description alone.

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?

Implicit usage: an agent learns the filing period (monthly/quarterly) is taken from company settings rather than passed as a parameter, which is useful routing context. However, there is no explicit when-to-use statement and no pointer to alternatives such as get_financial_overview for a broader picture, so guidance stays implied.

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