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

Goes well beyond the annotations: it discloses the monthly caps (4 educational / 2 promotional per course), the no-external-links rule for promotional emails, the default per-call confirmation with an opt-out, the requirement to confirm before reaching other people, and the needed Cotlet API key scope. This is exactly the operational detail an agent needs.

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?

Front-loads the core action and constraints well, but the second sentence ('Sends one message to the students enrolled in a course') largely repeats the first sentence's 'Email enrolled students', so not every sentence earns its place.

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 write tool with no output schema and only partial annotations, it covers limits, confirmation policy, external-recipient caution, and auth. Return-value behavior is not described, but the schema carries param detail and no output schema exists, so it is close to complete.

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 parameters are already documented. The description adds real meaning for `kind` by attaching distinct limits and link rules to educational vs promotional, going beyond the enum labels.

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?

States a specific verb (Email) and resource (enrolled students / announcement) and distinguishes the two modes (educational announcement vs promotional email). An agent can tell exactly what this does without opening the schema.

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?

Gives concrete use context: it sends one message to enrolled students, is bounded by monthly per-course limits, and describes the confirmation behavior. It doesn't name an alternative tool, but the sibling set offers no true substitute for this action, so the guidance is clear.

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