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

Beyond the annotations, the description discloses key behavioral traits: it re-validates the delivery area when date or postal code changes, atomically makes no changes if there's a problem, and rejects already-paid carts. These are critical side effects not derivable from the annotations alone. There is no contradiction with annotations.

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 compact, structured in three sentences: what it does, how to use it (partial update), and two important behaviors (delivery-area re-check, paid-cart rejection). Every sentence carries essential information with no redundancy or filler.

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 12-parameter update tool with no output schema, the description covers the essential context: partial updates, validation triggers, atomicity on failure, and rejection conditions. It is sufficient for an agent to invoke the tool correctly and anticipate outcomes. No meaningful gaps remain.

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 description lists the same set of fields as the schema and adds the general 'only changed fields' rule, but it doesn't add new per-parameter semantics beyond what the schema already supplies. It remains adequate without significantly enriching parameter definitions.

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 starts with 'Ändert einen bestehenden Warenkorb' (changes an existing cart), clearly distinguishing it from creating a new one. It then lists the specific fields that can be updated (delivery/pickup date, address, phone, email, greeting card, pickup time, payment method). This makes the tool's purpose unambiguous and differentiates it from siblings like create_cart and add_to_cart.

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 explicitly says 'Nur die Felder übergeben, die sich ändern' (only pass the fields that change), which is direct guidance for API usage. It also says 'statt einen neuen anzulegen' (instead of creating a new one), indicating when not to use this tool. However, it doesn't explicitly name alternative tools or provide a decision tree, so it stops short of full when-to-use-vs-alternatives coverage.

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