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), so the bar is lower. The description still adds real behavioral context: it enumerates what comes back (host, ports with encryption, login method, provider setup guide) and explicitly states it never asks for credentials, which is meaningful because sibling check tools do require creds.

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?

Three sentences, front-loaded with the usage trigger, then return contents, then the credential reassurance. No repetition of the title and no filler; every sentence carries information.

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 carries the burden of describing returns and does so concretely (host, encrypted ports, login method, setup guide). Combined with the credential note and provider examples, an agent has everything needed to select and call it correctly.

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 coverage is already 100% for the single provider_name parameter, so baseline is 3. The description adds value by enumerating valid providers including ones absent from the schema examples (Microsoft 365, Zoho, Amazon SES), helping the agent map user phrasing to a lookup value.

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+resource: retrieving outgoing SMTP server settings for a named provider, with concrete provider examples (Gmail, Outlook, Microsoft 365, SendGrid). It does not however explicitly distinguish itself from the closely-named siblings smtp_check (live connectivity test) or imap_finder (incoming counterpart), leaving that inference to the agent.

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?

"Use this when the user needs the outgoing mail (SMTP) server settings..." gives a clear triggering condition. There are no explicit exclusions and no named alternatives despite strong sibling overlap with smtp_check and imap_finder, so it stops short of full routing guidance.

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