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

No annotations are provided, so the description carries the full burden. It usefully discloses the blocking/waiting behavior and the 'unseen' selection semantics, but does not state what happens on timeout (error vs. empty return), nor that returning an email marks it as seen.

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?

Two sentences, front-loaded with the core behavior, then the motivating use case. Every clause earns its place with no redundancy.

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 two-param tool with no output schema, the description covers what is returned (email containing otp or verify_link) and the blocking constraint. Only the timeout-failure behavior is left unspecified.

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?

timeout_seconds has no schema description, and the description compensates by specifying the wait meaning up to that value. The delete parameter is documented in the schema ('Once deleted it is gone'), so the description adds value where coverage is missing.

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 and resource ('Return the next email you haven't seen yet') with the key qualifier that it blocks up to timeout_seconds. Clearly distinguishable from siblings like list_emails and read_email, which do not wait.

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?

Explicitly names the scenario ('Use after signing up somewhere to get the verification code (otp) or link (verify_link)'), which routes the agent correctly. It lacks an explicit when-not or mention of the delete/read alternatives, but the positive usage context is clear.

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