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

Beyond the single readOnlyHint=false annotation, the description discloses key behavioral traits: aggregation of identical services, daily breakdown attachment, exclusivity (a service can never appear on two invoices), idempotency via vorgangsnummer, and monthly quota consumption. This is rich, useful context for a mutating operation.

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?

Four dense sentences with no filler; each sentence adds distinct information: purpose, scoping default, aggregation behavior, exclusivity/idempotency, and quota. The core purpose is front-loaded in the first sentence.

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 tool without an output schema, this definition is largely complete: it covers purpose, defaults, idempotency, aggregation, and quota. Minor gaps remain, such as the default period when both von and bis are omitted and the behavior if validation fails.

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 100%, so the baseline is 3. The tool description adds real semantics on top: the default behavior when leistung_ids is omitted, the effect of verdichten on invoice positions and the attachment, and the role of vorgangsnummer as duplicate protection. It does not need to repeat the date formats already in 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?

The first sentence clearly states the action: turning one customer's open services into a validated e-invoice (XRechnung, PDF, ZUGFeRD). This distinguishes it from tools like leistungen_offen or rechnung_erstellen, but it never explicitly names a sibling alternative.

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?

The description gives clear context: use it to bill one customer's open services, optionally scoped by leistung_ids or a date range, and notes the account requirement in the title. However, it does not say when to prefer a different tool or when not to use this one.

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