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

Annotations already declare readOnlyHint and idempotentHint, and the description appropriately matches a non-destructive read. It adds important behavioral disclosure beyond annotations: the security warning that each address is a write credential for a folder and must not be placed in notes or summaries. This is valuable context the agent needs for downstream actions, not just for this tool.

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 compact yet information-dense: a clear action, the Pro restriction, the behavior, the return-field list, the Free-account behavior, and a security warning all fit in four sentences. The most actionable warning about secrecy is placed at the end with emphasis, and no sentence is wasted.

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?

Given zero parameters, no output schema, and annotations already covering safety/idempotence, the description is fully complete for invocation. It even provides return-field names and the Free-account empty-array case, which are exactly the context an agent needs to interpret results correctly. There is no missing information for selecting or calling this 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 has zero parameters and schema description coverage is 100%, so there is nothing for the description to add about parameter syntax. The description does, however, enumerate the return fields (id, label, address, destination, container_id, etc.), which meaningfully describes what the agent can expect in results even without an output schema. This exceeds the baseline for a zero-parameter tool.

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 ('List') and resource ('the user's email capture addresses'), and immediately clarifies it is Pro-only. It distinguishes the read/list behavior from sibling creation tools like email-addresses-create, so an agent can tell them apart without opening schemas.

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 provides clear context: mail sent to these addresses becomes a note in a bound folder, and Free accounts get an empty array. It also states when not to expect data, effectively guiding an agent selecting this tool versus alternatives. Although it doesn't name explicit alternative tools, the sibling list already contains email-addresses-create, and the description's focus on listing makes the usage context clear.

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