Send an email

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

With no annotations, the description carries the disclosure burden. It adds a meaningful behavioral constraint: 'from' must be on a domain verified in Maillog, and sandbox keys may only send to the address the key was issued for. However, it does not disclose failure behavior, delivery semantics, or other side effects beyond the act of sending.

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 two sentences long: the first states the purpose, the second states the key constraint. There is no filler, and the most important information is front-loaded before the caveat.

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 an 8-parameter write operation with no annotations and no output schema, the description is minimally adequate: it gives the core purpose and one critical precondition. It omits response/error behavior, the need to supply html or text, and any guidance about selecting this tool over list_emails, leaving clear gaps.

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 only 50%; from, to, html, and text have schema descriptions, while cc, bcc, subject, and reply_to do not. The description adds important meaning to 'from' by requiring a verified domain and to 'to' through the sandbox restriction, but it does not compensate for the wholly undocumented remaining 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 uses a specific verb and resource: 'Send a transactional email through Maillog.' The action 'Send' immediately distinguishes this tool from the read-oriented sibling list_emails, so an agent can tell them apart without inspecting the schema.

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?

There is no explicit when-to-use or when-not-to-use guidance. The phrase 'transactional email' implies the intended context, and the sibling list_emails is clearly a different operation, but no alternative or exclusion condition is named. Usage is only implied, not stated.

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