send_email

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

No annotations are provided, so the description carries the full burden. It discloses that sending is the core action and that replying enables threading (a behavioral detail). However, it does not mention potential consequences (e.g., email dispatch is irreversible) or requirements (e.g., authentication, rate limits). The threading detail adds moderate transparency.

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 a single sentence with no extra words. It front-loads the core purpose and then adds the key threading note. Every part earns its place; there is no redundancy or fluff.

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 (10 parameters, 4 required) and the presence of an output schema, the description does not need to explain return values. However, it is missing context about error handling, default account behavior, or size limits on attachments. The description is minimally sufficient but leaves gaps for a well-rounded understanding.

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%, but the description adds value beyond the schema: it explains that attachments support 'common file types (documents, images, archives, etc.)' and clarifies that in_reply_to enables 'proper threading'. The references parameter is also contextually tied to threading. This additional semantic information justifies a score above the baseline of 3.

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 action ('Send an email') and the resource ('using the specified account'). It highlights a key feature (replying with threading) that distinguishes it from sibling tools like add_email_account or delete_emails. The verb and resource are specific and unambiguous.

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 (sending new emails or replies) but does not explicitly contrast with alternatives. It lacks guidance on prerequisites (e.g., account must be configured) or when not to use it. The threading mention provides some context but no exclusions.

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