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

Annotations already declare write (readOnlyHint=false) and open-world behavior. The description adds the non-obvious deferred side effect (letter is only printed and sent after payment) and that the immediate return is a payment link, both of which matter for planning a multi-step flow.

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 short sentences, front-loaded with the action and its return value, followed by the payment-gating behavior and the document source. No filler or repetition.

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 no output schema, the description correctly discloses the key return (a Stripe payment link) and the payment-gated fulfillment, which is the essential mental model for an 11-parameter mutation tool. It omits edge cases such as link expiry or payment failure, but nothing critical for correct invocation is missing.

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 schema already documents every parameter including upload_id's origin and the pdf_base64 alternative. The description restates the same upload_id/pdf_base64 choice without adding format, size, or precedence detail, so it earns only the baseline.

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+resource (legt einen Briefauftrag an) and the distinctive return value (Stripe-Bezahllink), which separates it from the sibling pricing/status/upload tools. The description also names create_upload_link as the source of upload_id, tying it into the tool family.

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?

Provides clear operational context: an order is created now but printing/sending only happens after the user pays, which tells the agent this is the commitment step rather than a price check or status lookup. It does not explicitly say when not to use it or compare against get_letter_price/get_letter_status.

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