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

Annotations already declare idempotent, non-destructive, open-world behavior, so the safety burden is lighter. The description still adds real value beyond them by disclosing exactly what is attempted (connection, encryption, authentication) and the credential-handling policy ('Credentials are not stored'), which an agent may need to reassure a user about.

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 tight sentences with no filler; the restrictive usage condition and the no-storage guarantee are both front-loaded and immediately actionable. Slightly unusual to lead with the constraint rather than the purpose, but nothing is wasted.

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 five-parameter, all-required diagnostic tool with no output schema, the description covers what is tested and the outcome semantics (each of connection/encryption/auth either succeeds or not). It does not mention timeouts, network egress expectations, or failure modes, which are minor gaps given openWorldHint is annotated.

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 every parameter has its own description including examples (993 for SSL, enum values for encryption), so the schema does the heavy lifting. The description adds no parameter-level detail beyond that, making the baseline 3 correct.

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 and resource: connects to the IMAP server and reports whether connection, encryption and authentication succeed. This is functionally distinct from sibling imap_finder (which discovers settings) and smtp_check, so an agent can route correctly 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?

Gives an explicit gating condition - only when the user explicitly asks to test an IMAP login for a mailbox they control and supplies credentials - which functions as a when-not guard. It stops short of naming an alternative tool or describing what to do when the user only wants settings discovered, so it is not a full 5.

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