start_add_phone

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

With no annotations, the description carries the full burden of behavioral disclosure. It transparently explains the reverse OTP mechanism, that the system sends a message and the user replies, and details the exact return payload (session ID, deep_link, qr_code, qr_text). It also mentions the auth requirement. It does not cover expiration, follow-up steps, or failure modes, but the core behavior is well disclosed.

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 front-loaded with the tool's purpose and reverse OTP behavior, followed by necessary access instructions. It is slightly long due to the auth note, but every sentence contributes distinct, useful information without redundancy.

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 only one parameter and no output schema, the description covers the essential return values, the flow, and the authentication requirement. It doesn't explicitly mention the next step (e.g., polling get_add_phone_status), but that is inferable from sibling tool names and not strictly necessary for starting the process.

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 fully documents the single 'channel' parameter with an enum (telegram, whatsapp, sms) and a clear description. The tool description adds no additional channel-specific meaning beyond what the schema already provides, so the baseline of 3 applies.

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 and resource: 'Start adding a new phone number.' It also explains the reverse OTP flow and lists the return values, so an agent can immediately understand what this tool does and distinguish it from email or other verification tools.

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 clearly implies when to use the tool (when adding a phone number) and provides explicit access prerequisites: requires a Proof account, PROOF_API_KEY setup, or completing start_login first. However, it does not explicitly name alternative tools or state when not to use it, so it falls short of a 5.

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