List messages of an address

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

Annotations already declare readOnly, idempotent, non-destructive, so the safety profile is covered. The description adds genuinely new behavioral facts the annotations do not convey: a fixed 24-hour lookback window, newest-first ordering, and that message bodies are omitted from results. It could still note whether the 24h window is fixed or derived from a parameter.

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?

A single sentence front-loads the filtering/window constraint and ordering, then appends the sibling routing in parentheses. Every clause earns its place with no redundancy.

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 an output schema present, return values need no explanation, and the description covers the non-obvious behaviors (24h window, ordering, body omission). It is essentially complete for a simple filtered list tool; only the nature of the time window (fixed vs. relative) is left slightly ambiguous.

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%, with every filter (email, limit, unread_only, from_contains, subject_contains) documented in the schema itself. The description adds no parameter-level detail beyond that, so the baseline 3 applies when the schema carries the load.

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 gives a specific verb (List), resource (messages), recipient scope (an address), time window (last 24 hours), and ordering (newest first), then explicitly distinguishes itself from read_message. An agent can separate this from read_message without opening either 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?

It explicitly routes body-reading to read_message ('no body; use read_message'), which is a clear when-to-use-alternative. It does not address when to prefer wait_for_message or how this relates to the mailbox-list siblings, so it stops short of full when/when-not coverage.

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