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

Annotations declare readOnlyHint=false, openWorldHint=true, and destructiveHint=false. The description adds substantial behavioral context beyond annotations: a real email side effect, a per-address rate limit, hash-only storage, no added permissions, and a 30-minute completion window.

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?

It is a compact single paragraph that front-loads the optional-badge framing and the action. Every sentence adds a constraint, privacy detail, or follow-up instruction.

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 an open-world side-effect tool with no output schema, the description covers the key behavior, rate limits, privacy, and next step. It leaves response format and api_key usage to the schema and annotations, which is a minor gap.

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 50%: api_key has a schema description, but email does not. The description adds that the email must be controlled by the user and is hashed/rate-limited, but it does not explain the api_key parameter or add email format details 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?

It states the concrete action (sends a real email with a 6-digit code) and scope (address you control), and explicitly points to email_verify for completion. This makes it clearly distinguishable from the sibling verifier.

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?

It frames the tool as an optional badge and gives the follow-up path: finish with email_verify within 30 minutes, plus the max-3-per-day constraint. It does not state an explicit 'do not use if' condition, but the optional framing and constraints are sufficient for selection.

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