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

Beyond the annotations (which already declare readOnly and non-destructive), the description adds real behavioral value: it guarantees no password is ever returned, discloses a conditional warning when the domain's mail is hosted elsewhere, and states a security rule not to request passwords. No return-format or pagination detail, but for a read tool this is strong added context.

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 use case is front-loaded and the return contents are packed efficiently. Minor redundancy: the 'never a password' prohibition is stated twice (once informatively, once as an instruction), costing a bit of economy.

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 explaining returns and does so well by enumerating server settings, the certificate note and the conditional warning. The only gap is that it does not clarify what the response looks like when settings are unavailable.

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 100%, so both parameters (domain, email) are already fully documented in the schema. The phrase 'für eine Adresse der Domain' hints that email must belong to domain, but adds no format or validation guidance beyond the schema. Baseline 3 applies.

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 concrete verb (delivers) and enumerates the exact resources returned: IMAP/SMTP server settings, ports, encryption, username, certificate note and a provider-mismatch warning. This distinguishes it in substance from get_email_accounts or get_webmail_url, though it never names a sibling explicitly.

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?

Opens with an explicit triggering question ('Wie richte ich mein Postfach im iPhone/Outlook ein?') and routes the iPhone/Mac profile case to the panel instead (Reiter E-Mail → Auf Gerät einrichten). Clear when-to-use context, but no named tool alternatives or exclusions.

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