list_mail_messages

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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description goes further by disclosing ordering behavior ('newest first'), that full bodies are omitted, and how pagination works ('Pass the smallest message ID from a previous response to fetch older messages'). These are useful behavioral details beyond the structured annotation hints.

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 tightly organized: a one-line summary, a short clarification of return scope, clear Arg sections, and a Returns section. Every sentence adds value and there is no redundant or filler content.

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 three parameters stubby, the description covers identification of the mailbox, limits, pagination, output shape, and the relationship to sibling tools. Combined with the read-only annotations and output schema, an agent has everything needed to invoke and interpret the tool correctly.

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 0%, so the description carries full responsibility for parameter semantics. It explains mailbox_id as the mailbox database ID obtainable via list_mailboxes, limit as maximum count with a range and default, and cursor with a concrete usage pattern for fetching older messages. No parameter is left unexplained.

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 begins with a specific verb and resource: 'List messages in a mailbox, newest first.' It clearly distinguishes this tool from its sibling get_mail_message by noting it returns summaries without full bodies, and from list_mailboxes by specifying the mailbox_id source. The purpose is immediately actionable.

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 explicitly instructs when to use get_mail_message instead ('Use get_mail_message with a message ID to read the full content') and tells the agent to use list_mailboxes to obtain the required mailbox_id. It also explains pagination usage with cursor, giving clear operational guidance for calling this tool correctly.

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