send_email

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

With no annotations, the description carries the full behavioral burden. It usefully discloses the verified-domain prerequisite and the scheduling behavior. However, it does not mention irreversibility, delivery failure handling, or that scheduled emails can later be cancelled via a sibling tool.

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 short sentences, front-loaded with the core action, followed by parameter guidance and a constraint. Every sentence earns its place and there is no repetition or filler.

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 tool with six parameters and no output schema, the description covers the essential points: purpose, scheduling syntax, and sender-verification requirement. It is sufficient for correct invocation, though it could be stronger by explicitly pointing to send_broadcast for bulk campaigns and noting cancellation via cancel_scheduled_email.

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 67%, and the description mostly restates parameter details already present in the schema, such as scheduled_at relative phrases and the verified-domain constraint on from. It adds no new meaning for subject or text beyond the schema's minimal 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 states a specific verb ('Send'), a resource ('transactional email'), and the immediate/scheduled modes. The word 'transactional' clearly distinguishes this tool from sibling tools like send_broadcast and send_template_email.

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 implies when to use it by qualifying the email as 'transactional' and by explaining scheduling, but it never explicitly names alternatives like send_broadcast or send_template_email, nor does it state when not to use this tool.

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