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

Annotations already establish the safe read-only, closed-world profile, so the bar is lower. The description earns credit by disclosing what the check evaluates and the behavioral consequence that suppressed recipients are skipped by campaigns, though it says nothing about the shape of the result.

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 written sentences with zero padding; the action is front-loaded and the parenthetical about suppression plus the debugging use case each add distinct value.

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 single-parameter, read-only diagnostic with no output schema, the description covers what is checked and why an agent would call it. It could go one step further by hinting at what the response returns, but nothing essential for invocation is missing.

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?

Only one parameter and schema coverage is 100%, so the schema already documents 'recipient' as the address to check. The description adds no format, matching, or casing nuance beyond that, which is the expected baseline when the schema does the work.

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 ('check') and resource ('delivery status for a recipient address'), then enumerates exactly what is inspected: bounce, complaint, and suppression-list membership. No sibling in the list performs this diagnostic, so it is unambiguous where it fits.

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?

Clearly frames the use case ('did my email to X arrive?' debugging), which tells the agent when to reach for it. It does not name any alternative or state when-not to use it, but no sibling overlaps this diagnostic function, so the omission is minor.

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