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

Annotations declare readOnlyHint=false and destructiveHint=false, so safety is partly covered. The description adds genuinely useful non-annotation context: a Proof account is required, the client must be authenticated, and a session from start_login is a prerequisite.

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 is front-loaded in one sentence, with access prerequisites in a second short block. No filler, though the auth instructions are somewhat platform-specific for a reusable definition.

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 one-parameter, no-output-schema tool, the essentials (purpose, session prerequisite, auth requirement) are present. It omits resend limits/rate behavior and what the caller should do after resending, leaving a modest 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 100% and there is only one parameter, so the schema already documents session_id. The description only marginally extends this by clarifying the session must belong to an in-progress email addition, which is the right baseline-3 level.

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 ('Resend') plus resource ('OTP code') scoped precisely to 'an in-progress email addition', which cleanly separates it from verify_email_otp, submit_verification_code, and start_add_email.

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?

The in-progress-add-email precondition implies when the tool applies, and authentication guidance (authenticate the client or use start_login) is given. However, it does not explicitly state when NOT to use it, nor route to sibling alternatives such as verify_email_otp when the code arrives.

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