Get mailbox info, current time and rules

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description's 'changes nothing' largely restates destructiveHint=false; the only genuine addition is that it returns a JSON object and should be called once per session.

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 sentences, no padding. The first front-loads what the tool returns; the second carries the actionable ordering guidance. Every clause earns its place.

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 compensates by enumerating the contents of the returned JSON, which is enough to set expectations. It stops short of describing the shape or fields of the policies/limits, but for a read-only, zero-parameter helper this is largely complete.

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?

The tool takes zero parameters, so the schema has nothing to describe and there is no semantic gap for the description to fill. Baseline 4 applies for a parameterless tool.

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 names a precise verb and enumerates the specific resources returned: the user's own email address, current date/time, allowed senders/recipients, send limits, and outgoing review rules. This clearly separates it from every sibling, which all deal with individual messages or events.

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 states exactly when to call it ('once at the start of a session'), the ordering constraint ('before list_messages or send_message'), and the reason ('so you only write to allowed recipients'). No other sibling is in scope here, so no alternative needs discussion.

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