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

Annotations declare readOnlyHint=true, and the description aligns by stating it 'returns' a link rather than mutating anything. The description adds context about the customer clicking and paying, which clarifies purpose but not operational behavior (e.g., errors, state requirements, link expiry). Since annotations already cover the read-only nature, a 3 is appropriate.

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?

The description is two concise sentences in German, front-loading the primary action and outcome. Every word contributes to understanding the tool's function, with no fluff 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?

For a simple read-only tool with one parameter, the description is adequate but not fully complete. It does not specify the return format (e.g., URL string), error handling for non-existent carts, or any prerequisites. Given the absence of an output schema, a bit more detail would help agents use it correctly, but the description covers the core purpose.

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% because cart_id has a description ('ID des Warenkorbs'), but the tool description does not add any additional semantics beyond that label. It does not clarify format, required state, or example values, so the description adds no value beyond the schema, warranting the baseline 3.

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 clearly states the tool's action: returning a direct checkout link for an existing cart. It uses a specific verb ('gibt zurück' = returns) and resource ('Checkout-Link für einen bestehenden Warenkorb'), and the context of sibling tools (create_cart, add_to_cart, update_cart) makes it distinct as a payment-link retrieval operation.

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 provides no explicit guidance on when to use this tool versus alternatives. It does not mention that the cart must already exist, that this is for the payment step, or that it should be used after cart creation. An agent would have to infer usage from context, which is insufficient.

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