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

Annotations already declare readOnly and openWorld, so the description's added value is the refresh cadence (daily) and the staging limitation — real behavioral facts not in structured data. It does not say what an empty result means (untracked/not yet scanned) or whether results are paginated.

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?

Two tightly packed sentences plus the endpoint: return shape first, then operational caveats. No filler, front-loaded with what the caller gets.

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?

With no output schema, the description usefully enumerates the returned fields and the daily-update/staging constraints, which is enough to call it correctly. Minor gaps remain around empty-result semantics and response size for large jobs with tracking_detail enabled.

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 baseline is 3. The description's mention of 'per mail piece barcode' hints at the bar_code filter but does not explain tracking_type (IMB vs IMPB) or that tracking_detail expands per-piece scan history — both are left entirely to 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?

States a specific verb+resource ('USPS tracking for a submitted job') and enumerates the per-piece data returned (barcode, address, status, date, location), plus the underlying endpoint. It is distinguishable from click2mail_get_job_status/get_job_info by being piece-level carrier tracking, though it never names those siblings explicitly.

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?

'Tracking updates once a day, so one call per day is enough' tells the agent both the polling cadence and that redundant calls are wasted, and 'nothing is tracked on staging' gives a clear when-not condition. It stops short of naming which sibling to use instead when the agent wants submission status rather than carrier scans.

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