Send email

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

With no annotations provided, the description must convey behavioral implications. It discloses the environmental dependencies and that it works with any SMTP provider, which is useful. However, it does not state what happens on success/failure, whether it is idempotent, or any rate limits. It neither contradicts annotations (none) nor provides deep behavioral context, so a 3 is appropriate.

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, front-loaded sentence that states the purpose and the critical prerequisite. It is efficient with no fluff, though it could have added parameter details without becoming verbose. It earns a 4 for being compact and well-structured, but loses a point for skipping crucial semantic info.

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 five parameters, no output schema, and no annotations, the description is insufficiently complete. It fails to define the required parameters, the role of 'app', or the relationship between html and text (e.g., which takes precedence). An agent would need to guess parameter formats and meanings, making this tool difficult to use correctly.

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 0%, meaning the description must compensate for parameter meanings. The description does not explain any of the five parameters (to, app, subject, html, text). 'app' is especially ambiguous, and the distinction between html and text fields is unaddressed. With zero parameter guidance, the description fails to help the agent construct a valid invocation.

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'), resource ('transactional email'), and transport ('via SMTP'). It clearly distinguishes from sibling tools like push_send (push notifications) by specifying email, so an agent can identify the correct tool without ambiguity.

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 a clear prerequisite: the required environment variables (SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASS, MAIL_FROM) must be present in the app's env. It implies usage when sending transactional email, and notes any SMTP provider works. It does not explicitly mention when not to use it or name alternatives, but given the sibling list, the intent is unambiguous.

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