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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered; the description adds useful behavior beyond them by disclosing sort order (newest first) and that results are previews rather than full messages. It doesn't mention the default unread-only filtering behavior that could hide already-read mail, nor any pagination/limit behavior.

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?

Two tight sentences with the core capability front-loaded and the example queries placed after it as supporting context. Nothing redundant relative to the schema.

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 adequately conveys the return shape (recent messages, newest first, short previews). A quick-read tool with zero required params and full annotation coverage doesn't need much more, though noting that only previews are returned (full bodies require read_email) would close the last gap.

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 every parameter including the "today"/"7d" syntax and per-mailbox limit is already documented. The description only echoes the account scoping ("across all mailboxes (or one)") and adds no format or interaction detail, so baseline 3 applies.

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 (lists) and resource (recent inbox messages), plus scope (all mailboxes or one), ordering (newest first) and result shape (short preview). An agent can distinguish this from search_emails or read_email 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?

Offers concrete use cases ("has anything come in today?", "any new BoxCart emails?") that tell the agent when this tool fits. It doesn't explicitly name search_emails or read_email as the alternatives for deeper retrieval, so routing is implied rather than spelled out.

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