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

The description communicates that this records a mailing event and that the tracking data is used by the team to monitor delivery. Annotations already indicate it is not destructive, and the description adds a small amount of context beyond that, but it does not reveal whether repeated calls overwrite or supplement earlier marks.

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?

A single, well-structured sentence that is front-loaded with the main action and adds the key piece of guidance about the tracking number. No filler or repetition of schema details.

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?

Given the simple action, the presence of an output schema, and safe annotations, the description covers the essential trigger and purpose. The only meaningful gaps are the carrier parameter and a clearer applicationId mapping, which are minor for this operation.

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 only 33%, so the description carries more responsibility. It adds meaning for trackingNumber ('courier tracking number') and its purpose, but leaves carrier entirely unexplained and does not explicitly map applicationId to the corresponding ITIN application. This is partial compensation for the low schema coverage.

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 specific verb ('records') and a specific resource ('user mailed their signed W-7 package'). This clearly distinguishes it from sibling tools like itin_get_itin_mailing_instructions and itin_submit_itin_for_review.

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 clear context: call this after the user has physically mailed their signed W-7 package, and include a courier tracking number. It does not explicitly name alternatives or when not to use the tool, so it misses the top tier.

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