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

Annotations already signal a non-read-only, non-idempotent mutation. The description adds useful behavioral context: it is possible anytime before payment, and each call adds an additional item, which aligns with idempotentHint=false. No contradictions 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 and front-loaded with the core action, followed by concrete examples and constraints. Every sentence contributes useful information without 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 4-parameter mutation tool with no output schema, the description covers prerequisites, item source, and the payment-state condition. It does not describe the response shape or error cases, but the provided information is sufficient for selecting and invoking the tool correctly in most flows.

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 all parameters are already documented. The description repeats and reinforces the cart_id and variant_id source hints, but does not add meaningfully beyond 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 description states a concrete action: adding another item to an existing cart, with specific examples (second bouquet, vase, card, etc.). It clearly differentiates from create_cart by requiring an existing cart_id and from search_flowers by referencing its zubehoer list.

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 explicit context: it requires a cart_id from create_cart, only adds to an existing cart, and is allowed until payment. It does not explicitly mention update_cart as the alternative for changing the cart, but the usage context is clear.

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