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

Beyond the readOnly/non-destructive annotations, it discloses meaningful behavior: it performs a supplier NIP checksum validation when mode=mpp, builds a specific /VAT/IDC/INV/TXT message, never sends a payment, and requires no API key. That adds real value over the annotations, though it doesn't say what happens when the checksum fails.

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?

Three dense sentences with the core purpose front-loaded and no filler. Slightly information-packed with mode, checksum and API-key notes stacked, but every clause carries useful facts.

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 output schema covers return values, and annotations cover safety, so remaining gaps are parameter-level: with zero required params and anyOf amount types, the description should clarify which identifier to supply for zwykly vs mpp and whether amounts are required in split-payment mode. Adequate, but incomplete for an 8-param builder.

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 description coverage is 0% across 8 parameters, so the description must carry the load, but it only explains mode=mpp, supplierNip (checksum) and, implicitly, ksefNumbers/collectiveId/invoiceNumber. vatAmount, grossAmount and description are unaddressed, and the mutual exclusivity of the identifier fields is not stated.

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 and resource ('Build a Polish bank transfer title') and scopes it to carrying a KSeF invoice number or collective identifier. The scope statement and the clarification that it does not send a payment let an agent separate it from payment-execution siblings without opening the schema.

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?

Gives clear context: use for constructing transfer titles, with mode=mpp for split-payment titles. It also names one exclusion ('Does not send a payment'). It stops short of naming the sibling tools to use instead (e.g. export_transfer_batch for actually batching payments), so it is clear but not fully routing.

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