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

Beyond the annotations, the description discloses important behavior: passed is false when any post-unsubscribe marketing email arrives, run_id makes that failure affect the run, and transactional emails like receipts and password resets are excluded. It also explains the Lab-gated error condition, though it does not cover rate limits or full response structure.

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?

The description is dense but front-loads the core behavior and packs useful exclusions and prerequisites into a short space. The Lab sentence is slightly tangential at the end but still earns its place by preventing avoidable errors.

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 tool with no output schema and sparse annotations, the description gives enough detail to understand what is checked, what is excluded, what passed=false means, and how run_id affects the run. Some details such as exact return shape or behavior when no unsubscribe exists are left implicit, but the essential semantics are present.

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 parameter definitions are already well documented. The description adds some meaning by linking address to mark_unsubscribed and noting that run_id causes failures to fail the run, but it does not substantially expand beyond the schema for address or test.

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 states a specific check: for each sender the address unsubscribed from, it reports marketing emails that arrived afterward by id and elapsed time, while excluding content. It explicitly ties itself to mark_unsubscribed and distinguishes the verification role from the unsubscribe action.

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?

The description makes clear this is used after mark_unsubscribed to verify whether marketing emails still arrived, and it states the Labs prerequisite that must be enabled first. It does not name alternative checks such as check_delivery, but the context for using this specific tool is otherwise clear.

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