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 result feedback (mailbox_id, from_address) and size limits (1MB HTML, 7MB attachments). However, it does not mention idempotency, rate limits, or side effects of sending (e.g., whether sending twice is problematic).

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 paragraph of moderate length with clear sentences. It is front-loaded with the main action. While not using bullet points, it remains efficient and free of redundancy. Every sentence adds value.

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 (11 parameters, nested objects, enums), the description is comprehensive. It covers modes, mailbox selection, attachment limits, and result feedback. The absence of an output schema is compensated by describing what the result provides. Minor gaps in behavioral transparency prevent a 5.

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 the description adds value by explaining the two modes and how parameters relate. It clarifies the mailbox fallback behavior, template variables, and the in_reply_to threading, providing meaning beyond the schema.

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's purpose: 'Send an email' with two distinct modes (template and raw HTML). It specifies the resource and provides enough detail to understand its scope, though it doesn't explicitly differentiate from sibling tools like 'send_message'.

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 two modes and provides guidance on when to use each (template vs raw HTML). It mentions single recipient and mailbox targeting, and includes the required parameters. However, it lacks explicit guidance on when not to use this tool versus alternatives.

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