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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description still adds substantive context: the password is never returned, ai_permissions defines the AI's allowed write scope and that out-of-scope tools are refused, indexed_at has a 15-minute refresh window with newer mail unsearchable, and sync_errors is conditionally present. These are non-obvious behaviors an agent cannot get from the annotations.

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 tight sentences, front-loaded with the core action and the password caveat, then field semantics. Every clause carries information the agent would otherwise have to guess; nothing is redundant.

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?

Output schema exists, so enumerating returned fields is unnecessary, and the description instead supplies the interpretive context (permission scope, index freshness, conditional sync_errors) that matters for correct use. Only a brief note on what 'connection details' comprises or error behavior on an invalid account_id 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 coverage is 100% and the single parameter already documents its origin ('Id from list_mail_accounts'). The description adds no additional constraint or format detail for account_id, so the baseline 3 is appropriate.

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?

Specific verb + resource ('Show the connection details of one of your mail accounts') with a clear scope limitation (a single account, password excluded). The singular 'one of your mail accounts' implicitly separates it from list_mail_accounts, and the schema reinforces that by sourcing account_id from list_mail_accounts, but the description never names the 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?

Usage is only implied: the agent can infer this is the per-account detail lookup versus the list sibling, but there is no explicit 'use X when...' statement or exclusion. The rest of the description is spent on output-field interpretation rather than when-to-use guidance.

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