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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds genuine context beyond that: it requires a Shield login, threat-mode results are annotated with malware verdicts and CVEs, and results are ranked by the domain's own traffic.

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 tight sentences with the primary listing behavior front-loaded, followed by the threats-mode qualifier and the login requirement. Every clause carries information and there is no redundant restatement of the name or title.

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 three-parameter, no-output-schema read tool, the description covers both modes, the auth prerequisite and the threats-mode enrichment. Minor gaps remain around the return shape and whether days has any effect outside threats mode, which keeps it from a 5.

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 the schema already documents all three parameters, including the days default and 0 = all-time. The description reinforces the domain/includeThreats coupling and adds the ordering behavior, but adds little new parameter meaning.

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 names a specific verb and resource and clearly separates the tool's two modes: listing the caller's verified domains with package counts, or listing Shield-observed packages for one domain. It does not explicitly differentiate itself from the sibling shield_check_packages, so it falls just short of a 5.

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 states the selection rule for its own modes plainly: 'Omit [domain] to list domains with package counts' and 'With includeThreats, one domain's packages come back annotated...'. That is clear conditional guidance, but it gives no when-to-use/when-not guidance relative to sibling tools such as shield_check_packages or shield_watchlist_status.

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