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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds genuinely new behavioral context: it returns host, ports with encryption, and a provider setup guide, and it explicitly never asks for credentials. With no output schema present, disclosing the return shape is valuable; it does not mention error behavior for unknown providers, which keeps it from a 5.

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, no filler. The trigger condition leads, followed by what is returned and the credential-safety note — correctly front-loaded for fast decision-making.

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 single-parameter, read-only lookup with no output schema, the description supplies everything an agent needs: the trigger, the return fields, and the assurance that no credentials are required. Nothing material is missing.

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% for the single parameter, so the baseline is 3. The description adds a few provider examples (iCloud, Zoho) beyond the schema's list, but gives no guidance on name format, case sensitivity, or fallback when a provider is unrecognized.

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 — retrieving incoming mail (IMAP) server settings — and names the provider category (Gmail, Outlook, Yahoo, iCloud, Zoho). It is clearly distinguishable from the sibling tools smtp_finder (outgoing) and imap_check (connectivity testing), so an agent can route correctly without opening any 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 a clear triggering condition ('when the user needs the incoming mail (IMAP) server settings for an email provider') plus concrete provider examples. It does not explicitly name the adjacent alternatives (smtp_finder for outgoing, imap_check for testing a live server) or state when not to use it, so it stops short of full when/when-not guidance.

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