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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the side effect of sending an OTP and the return of a session ID, but it does not mention rate limits, idempotency, or that this only initiates the addition without completing it (though 'start' implies it). This is adequate but not comprehensive.

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 description is efficient: two concise sentences stating purpose and access requirements, with no redundancy or unnecessary detail. It is front-loaded with the main action and return value.

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 simple single-parameter tool that initiates an email addition, the description covers the essential information: what it does, what it returns, and prerequisite access. It could mention the next verification step, but that is implied by the session ID return and sibling tools like verify_email_otp.

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?

The schema already describes the email parameter with 100% coverage. The description adds a minor contextual note that the OTP is sent to this email, but it does not add significant meaning beyond what the schema provides. Baseline 3 is appropriate.

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 clearly states the tool's purpose: 'Start adding a new email address' and specifies it sends an OTP code and returns a session ID. This distinguishes it from siblings like start_add_phone and verify_email_otp, making it easy for an agent to select the right tool.

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 description provides usage context by stating the requirement of a Proof account and the authentication flow via start_login. It implicitly tells the agent to call this tool only after authentication, but it does not explicitly mention when not to use it or alternatives beyond the general 'start_add' pattern.

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