save_to_mailbox

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

With no annotations, the description tells that the tool is a pure IMAP operation (no SMTP needed), default folder is Drafts with \Draft and \Seen flags. It does not mention error handling or behavior if folder doesn't exist, but for a save operation this is reasonable transparency.

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 description is three sentences, each carrying essential information: purpose, comparison to sibling, and technical detail. No fluff or redundancy. Well front-loaded with the core action.

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?

Given the tool has 12 parameters, 100% schema coverage, and an output schema, the description covers the key behavioral aspects (IMAP-only, default folder/flags, relation to send_email). It does not explain return values (likely covered by output schema) or prerequisites like account existence, but is sufficient for typical use.

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%, baseline 3. The description adds value by noting that parameters are the same as send_email, clarifying the default flags (\Draft, \Seen) beyond the schema's default values, and explaining the IMAP nature. This helps disambiguate parameter usage.

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?

The description clearly states the tool composes and saves an email to an IMAP folder, with a specific example (Drafts). It distinguishes itself from the sibling send_email by noting 'saves instead of sending' and 'Pure IMAP operation — works without SMTP configuration'. The verb 'save' and resource 'IMAP folder' are explicit.

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?

The description provides context on when to use: when you want to save rather than send, and when SMTP is unavailable. It implicitly contrasts with send_email by saying 'Same parameters as send_email, but saves instead of sending'. However, it does not explicitly state when not to use or list alternative tools.

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