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

The readOnlyHint annotation already establishes that this is a safe read operation, and the description consistently says 'Read' while adding the scope of what is read. It does not go further to mention auth requirements, data freshness, or other behavioral caveats, but the output schema covers return details.

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 a single short sentence with the key verb and resource front-loaded. There is no filler or redundant information, making it easy for an agent to parse quickly.

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 zero-parameter, read-only tool with an output schema and readOnlyHint, the description covers the essential selection information. It is slightly incomplete only because it does not direct the agent away from semantically adjacent siblings like inbox.

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?

This tool has zero parameters and an empty input schema, so there is no parameter meaning for the description to clarify. The baseline for parameterless tools is 4, and the description sufficiently signals that no inputs are needed.

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 uses the specific verb 'Read' and names the resource ('your mailbox') plus the data returned (expiry, allowed sender IDs). This makes its purpose clear, though it does not explicitly differentiate it from sibling tools like inbox or get_connection_info.

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?

No guidance is provided about when to use get_mailbox versus alternatives such as inbox, update_mailbox, or get_connection_info. The read-only wording implies it is for retrieving mailbox settings, but there are no explicit use cases, exclusions, or conditions.

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