Mail connection health

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

The description adds substantial behavioral detail beyond the readOnlyHint annotation: it discloses the exact return fields ({ok, source, kind, message, latency_ms}), the presence of credential information, and explicitly states it never returns the password. This security-relevant transparency is valuable and goes beyond what annotations convey.

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 compact and front-loaded with the primary purpose, followed by the return shape, a critical security guarantee, and a clear usage directive. Each sentence adds distinct value; there is no filler or repetition of schema content.

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 health check, the description is complete: it explains what the tool does, what it returns, what it will never return, and when to invoke it. The existence of an output schema covers further return details, and no other operational information is missing for correct invocation.

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 has no parameters, so the baseline is 4. The input schema is empty and thus fully covers the parameter space. The description adds no parameter-specific detail because none is needed; instead it focuses on return semantics, which is appropriate for this zero-parameter 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 states a specific verb and resource: 'Check that the mailbox is reachable and the credential works.' This clearly distinguishes it from sibling tools like imap_list_mailboxes or imap_search_messages, which perform different operations on the same domain. The health-check purpose is immediately unambiguous.

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?

The description provides explicit contextual guidance: 'Run this first when anything else fails.' This tells the agent a clear triggering condition, and the 'first' implies a diagnostic-before-action ordering. It does not mention when not to use it or name alternatives, so it falls short of a full 5.

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