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

Beyond the annotations, the description discloses a non-obvious behavioral trait: the recipient address is sent directly to the fulfillment provider and is never visible to the agent. This adds meaningful privacy and side-effect context that the schema and annotations do not express.

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 only two sentences, with the core action stated first and the most valuable privacy detail second. Every sentence carries necessary information with 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?

For a side-effecting tool with fully documented parameters and annotations signaling destructive/open-world behavior, the description covers the essential precondition (delivery token) and the address-handling nuance. It does not describe post-call confirmation, but no output schema exists and the tool's role as a terminal action is clear.

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 coverage is 100%, so the baseline is 3, but the description adds important semantic context: it explains why no address parameter exists and clarifies that the delivery token is the handle for the out-of-band recipient address. This goes beyond the schema's per-parameter descriptions.

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 precise action ('Fulfill a handwritten card') and ties it to a concrete prerequisite ('using a delivery token returned by resolve_delivery'), which distinguishes it from the sibling tools. It is clearly the final send step rather than listing, permission, or delivery resolution.

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 indicates when this tool is appropriate: after resolve_delivery has produced the delivery token. It does not spell out when not to use it or mention the list/permission siblings, but the workflow context is strongly implied.

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