list_messages

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds real behavioral context beyond that: results are compact cards rather than full bodies, they are ordered newest first, and critically that reading does NOT mark anything seen — a non-obvious side-effect guarantee relevant to a mailbox 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?

Two tightly packed sentences with zero filler; the core scope and return shape are front-loaded and the alternative tool plus the seen-state caveat follow immediately after.

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?

Although no output schema exists, the description compensates by enumerating the returned card fields (sender, subject, preview, seen state, attachments) and the ordering. Combined with full parameter coverage and clear annotations, an agent has everything needed to call this 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 100% and the enum for kind is fully documented in the schema, so the baseline is 3. The description restates the messages/activity split but adds no format, default, or interaction detail beyond what the schema already provides.

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 (List) and resource (messages/activity log in a workspace) and grounds it in the UI surface ('the portal's Activity tab'). It also names the sibling that returns full content (get_message), so an agent can separate it from adjacent tools without opening a 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?

Explicitly routes the agent to get_message 'for a full body' and clarifies that reading does not mark items seen, implicitly contrasting with mark_messages_seen. It does not, however, say when to prefer this over other listing siblings (list_attachments, list_payments, list_tasks) or address the activity vs messages choice in prose beyond the schema.

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