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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds useful context: the data comes from the Ministry of Finance and bank_account lookups verify ownership as of a date. It omits behaviorally relevant details such as what happens when a NIP is not on the whitelist, whether results are cached, or rate limits.

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?

Two sentences, zero filler. The core action is front-loaded and the second sentence is a dense enumeration of the accepted parameter combinations, each clause earning its place.

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?

There is no output schema, so the description carries the burden of telling the agent what comes back. It hints at results ('find who owns it', 'verify the account belongs to that NIP') but never states the returned fields — e.g. whether an account list, VAT status or company name is included. Adequate for invocation, incomplete for interpreting results.

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 only 50% — nip and regon are undocumented in the schema — and the description compensates by defining the role of nip, regon and bank_account and how they combine. The date parameter is already documented in the schema, so the description rightly does not repeat it, but it also adds no format or range detail of its own.

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 (query) and a specific resource (Ministry of Finance VAT white list), and the title pins it to the Polish Biała lista. An agent can distinguish it from vies_check (EU VAT) and find_company by resource, though no sibling is named explicitly, which keeps it 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?

Explains the accepted input modes precisely: nip, optionally with bank_account to verify account ownership on a date; regon alone; or bank_account alone to find the owner. That is genuine invocation guidance, but it does not say when to reach for this rather than vies_check or contractor_due_diligence, so no exclusions are given.

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