Send an email

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

It discloses the async acceptance semantics, the non-blocking return behavior, and the idempotency mechanism beyond what annotations provide. This is valuable behavioral context for an agent deciding how to handle responses and retries.

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 focused sentences with no filler. The most important behavior (queued, returns immediately) is front-loaded, followed by follow-up guidance and idempotency advice.

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 9-parameter mutation tool with no output schema, the description covers the key operational concerns: side effect, async behavior, return value, and retry safety. It does not mention prerequisites like domain verification, but the schema and sibling tools partially mitigate that gap.

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 89%, so the schema already documents most parameters. The description adds meaning around idempotency_key and the return id, but does not need to compensate for missing parameter documentation.

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 ('Queue'), a clear resource ('a transactional email'), and the result ('return its id'). It distinguishes this tool from the sibling vaemail_get_message by clarifying the queue-then-deliver flow.

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 clearly explains when to call this tool (to queue a send) and directs the agent to vaemail_get_message for delivery status. It also gives concrete retry guidance via idempotency_key, though it does not explicitly list exclusions or alternatives for other scenarios.

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