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

Annotations show readOnlyHint=false and destructiveHint=false, and the description adds real context beyond them: it persists a PDF artifact with request IDs, timestamps and hashes, requires an API key, and explicitly states it does not send a payment. That resolves the key ambiguity (write side effect vs. money movement). Retention/location of the stored PDF is not described, keeping it below 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?

One dense sentence front-loads the trigger, the checks, and the artifact; the trailing clauses (API key, no payment) are useful disambiguators. The stacked parentheticals make it slightly breathless but nothing 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?

With an output schema present and annotations covering safety, the description only needs to carry the workflow and the side-effect intent, which it does. The gaps are the undocumented invoice/currency inputs and the storage location/lifetime of the PDF, both of which matter for a due-diligence 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 coverage is only 33%, so the description must compensate, and it partially does by implying the nip, account, payment date and amount (via the 15 000 PLN rule) inputs. It says nothing about invoice or currency, leaving two parameters without guidance in either the schema or the description.

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 specifies concrete verbs and resources: verify NIP/bank account against the MF VAT white list, check KRS and VIES, and store a PDF proof. That makes the tool's composite nature clear. It doesn't explicitly say how it differs from the overlapping siblings (check_vat_whitelist, vies_check, get_krs_extract), so differentiation is only implied.

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?

"Before paying a Polish contractor" is a clear trigger scenario that tells an agent when to reach for this tool. It does not state when not to use it or name alternatives such as the individual check tools, so the guidance stops short of full routing.

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