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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered structurally. The description adds genuinely useful domain semantics — that these addresses' mail to support is being dropped — which is more than the annotations convey. It still omits any sense of result size or pagination behavior for the listing.

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 short clause with no filler, and the defining characteristic (spam-marked, mail dropped) is front-loaded. It is efficient but so terse that it reads as a label rather than an instruction, leaving the action implicit.

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 zero-parameter, no-output-schema listing tool with rich annotations, the definition is close to sufficient — the agent needs only to know what the list contains. What is missing is the explicit action ('list') and any indication of whether the result can be empty or large, which is cheap to state in a list tool.

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?

The tool takes no parameters, so per the baseline there is nothing for the description to disambiguate. The schema is empty and the description does not need to compensate.

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 is a noun phrase defining the resource ('email addresses marked as spam, whose mail to support is dropped') rather than stating the action. It never says the tool lists or returns them, so the agent must infer the verb from the tool name. It does distinguish the domain concept from generic suppression lists, which helps somewhat.

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?

No guidance on when to call this versus alternatives. Siblings such as get_suppression_summary, list_external_mail, and unblock_sender are adjacent in the same domain, and the description does none of the routing work to say which one an agent wants. Zero parameters means there is also no condition under which it should be invoked.

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