save_to_mailbox

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

The description goes beyond annotations by disclosing specific behaviors: default mailbox/flags, no SMTP dependency, and how ambiguous APPEND responses are handled. These details are not available in the annotations, adding significant value.

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?

Each sentence delivers distinct, useful information without fluff. It front-loads the primary purpose, then covers differentiations, defaults, operational context, and an edge case—all in five tight sentences.

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's complexity (12 params, 4 required) and the presence of an output schema, the description covers the necessary context: what it does, how it differs from send_email, when to use it, and notable behaviors. It is sufficiently complete for an agent to decide and invoke 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?

Though schema coverage is 100%, the description adds meaning by explaining parameter relationships (shared with send_email, added mailbox/flags, unsupported reply_to) and the default flag values for mailbox and flags. This helps the agent understand parameter purpose beyond schema descriptions.

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 opens with a clear verb+resource: 'Compose an email and save it to an IMAP folder.' It explicitly contrasts with send_email by noting it shares parameters but adds mailbox and flags, and does not support reply_to, which clearly distinguishes it from the sibling tool.

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?

It provides explicit usage context by naming send_email as an alternative and stating this is a pure IMAP operation that works without SMTP configuration. The default folder and flags further clarify when this tool is appropriate (e.g., saving drafts not sending).

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