send_message

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

No annotations are provided, so the description carries the full burden. It discloses immediate sending, the save_to_sent_items default, the 3 MB attachment size limit, the mailbox default, and the exact return payload. It does not cover auth requirements, rate limits, or failure modes, but the main side-effects and constraints are visible.

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 opens with a one-sentence purpose, then uses a compact, scannable Args list with defaults and constraints, followed by the return shape. Every line adds useful information; there is no filler or repetition of schema-only details.

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?

Despite having no output schema and no annotations, the description is complete enough for an agent to invoke the tool correctly: it explains every parameter, key constraints, defaults, and the expected return. The only omissions are error/edge-case behavior and explicit sibling routing, which are handled by other dimensions.

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 description coverage is 0%, and the description compensates by documenting all nine parameters: required non-empty 'to', defaults for body_type and save_to_sent_items, optional cc/bcc, attachment object shape with size limit, and mailbox default. This adds substantial meaning beyond the bare schema.

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 states a specific verb and resource: 'Send a new message immediately.' The qualifiers 'new' and 'immediately' distinguish it from draft, reply, forward, and scheduled-message siblings, so an agent can tell what the tool does without needing to inspect other definitions.

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 opening sentence gives clear operational context: use this when you want to send a new message immediately. It does not explicitly name alternatives like create_draft, reply_message, or forward_message, nor does it give when-not-to-use guidance, so it falls short of a full 5.

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