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

Annotations only cover the safety profile (readOnlyHint=true, destructiveHint=false), and the description adds real behavioral context: the 25-second wait bound and, more importantly, the 'sender-verified' filter that constrains what will be returned. It stops short of describing timeout behavior (empty result vs. error) or any rate limits, so not a 5.

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 tight sentences with the core behavior front-loaded and parameter guidance second. The 'up to 25 seconds' wording duplicates the schema's default/maximum, a small redundancy, but nothing is wasted overall.

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 4-parameter blocking-wait tool with no output schema, the description supplies the essential mental model: what it waits for, how long, and how to avoid stale codes. The one meaningful omission is what the agent should expect when the wait expires without a match.

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%, so the description carries the load and does so for three of four parameters: 'wait' (up to 25 seconds), 'since' (your sign-up start time, used to reject older codes), and 'from_domain' (the expected service). Only the required 'to' parameter is left unexplained, a minor gap given the otherwise strong compensation for the coverage hole.

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+resource ('Wait ... for a sender-verified code') and scopes the behavior with the 25-second cap, so an agent knows this is a blocking poll for an inbound code. It does not explicitly contrast itself with the similar sibling wait_for_link, which is the only thing keeping it from a 5.

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 gives conditional guidance for two parameters ('set since to your sign-up start time to avoid an older code, and from_domain to the service you expect'), which implies a sign-up verification flow. However, it never says when to choose this tool over wait_for_link or list_recent_mail, nor what to do if no code arrives within 25 seconds.

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