send_email

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

No annotations are provided, so the description carries the burden of behavioral disclosure. It only says 'Send an email via Resend' without revealing that this is an external side-effecting operation, potential delivery failures, authorization requirements, or that sending cannot be undone. This is a meaningful omission for a tool that triggers an external action.

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, concise sentence that immediately states the action and target. There is no redundant or irrelevant content, and it is front-loaded. While it lacks depth, brevity is a strength here.

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?

With 9 parameters, 3 required, and an important external side effect, the description should provide context about the operation's scope, limitations, or typical use cases. None is given. The output schema exists, so return values are covered, but the description leaves the tool's role and edge cases unexplained.

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 description coverage is 100% and the schema already provides clear descriptions for all parameters. The tool description adds no extra meaning beyond the schema, so the baseline score of 3 applies.

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') and resource ('email via Resend'), clearly distinguishing this tool from siblings like create_contact, list_emails, and get_email. The action is unambiguous and cannot be confused with other tools.

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 provides no guidance on when to use this tool versus alternatives. It does not mention when to send an email, prerequisites, or exclusions (e.g., 'Use for transactional emails only'). The user must infer usage solely from the tool name.

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