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

Adds substantial context beyond the annotations: confirmation-by-default behavior, the human-in-the-loop requirement because the action reaches other people, the fact that nothing is transmitted until a separate send call, and the Cotlet API key requirement. It still omits reversibility (whether an issued invoice can be voided/renumbered), which matters for a mutation where destructiveHint=false.

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?

A single dense paragraph that front-loads the core action and then packs the constraints; nearly every sentence carries information. Minor cost is density/readability, and the '"Wystaw"' reference adds little for an English-speaking agent.

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 multi-param mutation with no output schema, the description covers the essential behavior (issuance semantics, required line shape, send flow, auth, confirmation). It would be stronger if it mentioned what is returned (invoice id/number) since no output schema exists to fill that gap.

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%, so the schema already documents all 8 parameters and the baseline is 3. The description adds real meaning beyond it by enumerating required line fields and noting that non-exempt lines may additionally need a PKWiU code, a requirement absent from the schema.

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 ('Issue a domestic invoice for a contractor with one or more lines') and clarifies the operation mode ('next number in the series, the same as "Wystaw"'). It also distinguishes the issuance step from the separate send steps (send_invoice_to_ksef / send_invoice_email) that siblings perform, so an agent can tell it apart from save_invoice_draft.

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 post-call flow ('not sent to KSeF or to the buyer until you call send_invoice_to_ksef or send_invoice_email') and gives a clear usage rule ('Reaches other people: confirm with the user before each call'). It does not, however, explicitly say when to choose this tool over ifirma_save_invoice_draft, leaving that selection to inference.

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