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

Goes well beyond the readOnly/non-destructive annotations by confirming no write occurs and describing the output shape (errors and warnings plus a summary with deadline) and the concrete failure classes detected. It omits severity semantics or whether results block submission, so not a 5.

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 core purpose and read-only nature, then parameters. The long parenthetical check list is dense and slightly hard to scan, but every item names a concrete validation, so little is wasted.

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 7-parameter, no-output-schema tool it supplies purpose, defaulting behavior, period selection rules, and a description of what the result contains. Remaining gap is the undocumented okec and cisloUfo parameters, which an agent cannot reason about from the definition alone.

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?

Adds real meaning for companyId defaulting and for month-vs-quarter selection by payer type, which the 71%-covered schema only partially expresses. However, okec and cisloUfo are left unexplained in both schema and description, so the gaps are not fully closed.

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 action (period check before VAT filing) plus the crucial disambiguation 'nic neuklada' (saves nothing), which separates it from generate_vat_filing, submit_vat_filing and correct_vat_filing in the sibling list. The parenthetical enumeration of what is checked further pins down scope.

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?

Explicitly frames usage as a pre-submission check ('pred podanim DPH') and gives payer-type routing rules (monthly -> month, quarterly -> quarter) plus the default-company behavior. It does not explicitly say when to skip it or name an alternative validator, so it falls short of a 5.

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