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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds useful context beyond annotations: it requires a connected account, lists what is returned (status, ETA, shipment id, checkpoints), and notes that supplying the carrier speeds up lookup. It does not describe failure modes or rate limits, but it is strong for a read-only lookup.

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?

Four sentences, each earning its place: purpose/scope, return values, prerequisite, and alternative/optional-parameter note. It is front-loaded with the core operation and contains no redundancy.

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?

There is no output schema, but the description compensates by naming the key return fields. It covers the account prerequisite, the alternative tool for no-sign-in tracking, and the optional carrier optimization. An agent has everything needed to invoke it correctly.

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 schema already documents both parameters. The description adds value by clarifying the account context for the lookup and that the carrier parameter is optional but improves performance, which is not in 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 specific verb and resource ('Look up the live status and checkpoint history of a parcel') and clearly bounds scope to the signed-in account. It explicitly distinguishes itself from the sibling track_package, so an agent can select correctly without opening either schema.

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?

It gives explicit when-to-use guidance ('on the SIGNED-IN account'), names the alternative ('track_package') and the exact condition for choosing it ('to track any parcel without signing in'). It also states the account-connection prerequisite.

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