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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuine domain context (suppressed recipients are skipped by campaigns), but it says nothing about the shape or fields of the returned status, which matters since there is no output schema.

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: the core check is front-loaded and the debugging rationale follows. Every clause earns its place with no restatement of the name or schema.

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 one-parameter read-only lookup, the description covers the check's meaning, the suppression consequence, and the agent's likely motivation. It lacks any indication of what the response contains, which is the only notable gap given no output schema exists.

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% with a single well-described 'recipient' parameter, so the schema does the heavy lifting. The description adds no semantics beyond it (e.g., behavior with aliases, case sensitivity, or unknown addresses), so the baseline 3 applies.

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 and resource (check a recipient's delivery status) then enumerates exactly what is checked: bounce, complaint, and suppression-list state. No sibling in the list covers this capability, so an agent can route to it without ambiguity.

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?

Gives a concrete use case ('did my email to X arrive?' debugging) that tells the agent when this tool is the right call. It stops short of naming a sibling to use instead when the question is about message content rather than delivery.

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