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

Annotations already indicate destructive/read-only hints, and the description adds important behavioral context: it sends an email, returns a session_id (not a token), and discloses the exact email subject line for retrieving the code. This is valuable and does not contradict the annotations.

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 five sentences, each earning its place: purpose, return value distinction, email subject info, and usage timing. It is well-structured and front-loaded with the primary action.

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?

Given the tool's complexity and the presence of an output schema, the description is complete: it explains what happens, what is returned, how to retrieve the verification code, and when to call it. It fully supports the agent in selecting and using the tool effectively.

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 input schema has 100% parameter description coverage, so the schema already documents each field. The description only says 'providing their contact information' and does not add new parameter-level details. Baseline 3 is appropriate since the schema carries the heavy lifting.

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 a patient session by providing their contact information. Sends a 6-digit verification code.' It specifies the action (start), the resource (patient session), and the side effect (sending a code). It also distinguishes itself from siblings by explaining the session_id flow and that it is not a token.

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?

Explicit usage guidance is provided: 'Call this when the patient is ready to proceed with their medical intake — after browsing medications and checking eligibility.' It also states 'No authentication required' and describes the next step (use with auth_verify_otp), making the usage context clear.

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