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

Goes well beyond the annotations by disclosing the daily rate cap, the unconfirmed-address precondition, the suppression/opt-out guard, and the downstream consequence (utility emails do not reach the owner until Confirm is pressed). It also documents the auth model in detail, including that a passport_token path returns signature_required — a failure mode the agent would otherwise hit blindly.

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 core action and its consequence are front-loaded, and every clause carries information. It is dense with nested parentheticals and semicolon-chained constraints, though, which makes it slower to scan than it needs to be for a one-parameter tool.

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 zero-required-parameter, no-output-schema tool with annotations covering safety, the description supplies auth requirements, rate limits, preconditions, and error behavior — nearly everything needed to call it correctly. It omits only what a success response looks like or how to resend after the daily window.

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% and there is only one optional parameter, so the schema already carries the mechanics of passport_token. The description still adds real value by explaining when that parameter applies ("only if you have no app sign-in and cannot send a header") and that it will fail with signature_required — semantics the schema field alone does not convey.

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 — send the owner the one-time confirmation email — and immediately clarifies what that email authorizes ("Allow your AI agent to email you?"). It is clearly distinguishable from sibling email senders like ask_human or check_emails, which do not confirm the owner's address.

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 explicit preconditions: only while the address is unconfirmed, at most once per owner per day, and never after they unsubscribed. What's missing is routing to siblings — it never says to use get_email_check or check_emails first to verify confirmation state, so the agent must infer that step.

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