send_email

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

No annotations exist, so the description provides transparency about domain verification requirements and the non-silent failure for unverified domains. It also mentions the sandbox sender behavior. It does not cover all edge cases but is sufficient.

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 concise with three sentences, each adding distinct information. The purpose is front-loaded, and there is no redundant content.

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 complexity of 10 parameters and no output schema, the description covers the core workflow and key constraints. It lacks details on return values or advanced error handling, but is complete enough for typical usage.

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%, so baseline is 3. The description adds value by explaining that html/text can be both or either, and providing context on from_email verification and the sandbox sender. It enhances understanding of key parameters.

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 sends a transactional email via Send16, with specific use cases (OTPs, receipts, alerts). This distinguishes it from siblings like send_broadcast and send_event.

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 explains when to use (transactional emails) and provides context for text-only sends. It offers guidance on verified domains and a sandbox option for first-time sends, but does not explicitly contrast with all sibling tools.

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