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

Annotations are present and the description adds behavioral context beyond them, such as the requirement for a verified sender domain and the monthly email limit. No contradiction with annotations.

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, clear sentence that efficiently conveys the tool's purpose, key features, and constraints. No unnecessary information.

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 tool's moderate complexity (6 parameters, 2 required) and the presence of an output schema, the description covers the essential usage context, requirements, and limits adequately.

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?

Input schema has 100% description coverage for its 6 parameters. The description mentions 'plain text or HTML body' and 'multiple recipients', which aligns with the schema but does not add significant new semantics beyond what the schema already provides.

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 transactional email) and lists key features (plain text or HTML, multiple recipients, reply-to). It is easily distinguished from sibling tools like 'email.transactional.status' which is for checking status.

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 includes a prerequisite ('Requires verified sender domain') and a usage limit ('3,000 free emails/month'), which help guide appropriate usage. However, it does not explicitly state when not to use it or mention alternatives.

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