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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantive behavior beyond them: empty-array return when none exist, the meaning of accepting_mail: false (mail currently being dropped), and a security warning that each address is a write credential for its folder. That last point is a genuine operational constraint an agent would otherwise miss.

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?

Purpose is front-loaded and the following sentences each carry load (return fields, edge cases, security). The enumerated field list is slightly long but justified since no output schema exists to document the response.

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?

With no output schema, the description compensates by enumerating the returned fields (id, label, address, destination, container_id, team_id, tags, notes_count, last_received_at) and documenting the empty-array and accepting_mail edge cases. Nothing an agent needs to call and interpret this tool 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?

The tool takes zero parameters, so the schema is trivially complete and there is nothing to disambiguate. Baseline 4 applies for a no-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?

States a specific verb and resource ('List the user's email capture addresses') and immediately explains what those addresses do, distinguishing this read tool from the sibling email-addresses-create. An agent knows exactly what it retrieves without opening any schema.

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?

Usage is implied by the listing semantics, but there is no explicit guidance on when to reach for this versus email-addresses-create or other container/folder tools, and no stated prerequisites. Minimum viable: the verb makes the context obvious, nothing more is provided.

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