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

Annotations already mark it read-only/idempotent, but the description adds valuable context: the shared-account caveat (list includes other callers' inboxes), the return structure with pagination, and the field details. This goes beyond annotations and helps the agent understand side effects and scope.

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 slightly long but every sentence contributes: purpose, return fields, pagination, shared-account warning, and sibling references. Front-loaded with the main purpose. Could tighten wording but remains efficient.

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 list operation with an output schema, the description covers return fields, pagination, scope caveat, and alternatives. It is complete for an agent to call correctly, with no missing critical information.

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 descriptions for all four parameters (limit, ascending, page_token, Authorization). The description mentions pagination with next_page_token but does not add semantics beyond the schema, so baseline 3 is appropriate.

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?

Clearly states 'Lists every inbox in the AgentMail account' with specific verb and resource, and distinguishes from get_agentmail_inbox (single) and post_agentmail_inbox (create).

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?

Explicitly names alternatives: 'Use get_agentmail_inbox for one inbox you already know the id of, and post_agentmail_inbox to create one.' Also warns that the list is not scoped to the caller, which is crucial for selecting this tool.

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