send_message

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

With no annotations, the description carries the behavioral burden. It clearly discloses that the email is sent irrevocably and immediately: 'This goes out the moment it runs — the client should confirm first.' It also notes local file attachments. It doesn't mention failure behavior or permissions, but the core irreversible side effect is well communicated.

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 sentences, each earning its place: immediate behavior, user confirmation requirement, and the alternative tool. The most important operational fact—immediate sending—is front-loaded first.

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?

For a sending tool with no annotations and no output schema, the description covers the critical execution context: the action is immediate, irreversible in practice, and should be confirmed by the client. It also provides the sibling alternative. It doesn't describe return values or error conditions, but these are less critical for an email-send operation.

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 71% and the schema already documents to, body, html, subject, and attachments. The description adds only that attachments are local files, which is slightly redundant with the schema. It does not clarify cc/bcc semantics, but those parameter names are reasonably self-explanatory. Overall the description adds minimal meaning beyond the 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 uses a specific verb and resource: 'Send a new email immediately.' It clearly distinguishes this from reply, forward, and draft tools by emphasizing 'new email' and 'immediately.' An agent can confidently identify what the tool does and how it differs from siblings.

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 explicitly tells the agent when not to use this tool: 'To let a human review before sending, use create_draft instead.' This is a direct, usable routing instruction that names the alternative and the condition that selects it.

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