register_phone

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 only states the action and PIN, but does not disclose side effects, permissions required, rate limits, or what happens after registration. This is insufficient for a state-changing operation.

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 a single, clear sentence with no wasted words. It is front-loaded with the action and resource. However, it is slightly too terse given the complexity of the operation, earning a 4 rather than 5.

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?

The tool has no output schema, no annotations, and a state-changing purpose. The description explains what it does but omits when to use it, prerequisites, or any expected result. This is inadequate for an agent to invoke it confidently in a sequence of related steps.

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%, with both parameters having descriptions. The description merely repeats the '6-digit PIN' detail already in the schema and adds no new meaning for data_localization_region. This meets the baseline but adds no extra value.

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 a specific action ('Register') on a specific resource ('WhatsApp Business phone number') with a key requirement (6-digit PIN). It distinguishes from sibling tools like request_verification_code, verify_phone_code, and deregister_phone.

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?

No guidance is provided on when to use this tool versus alternatives. It does not mention prerequisites such as needing a verification code first, nor does it explain the relationship to request_verification_code or verify_phone_code. The description implies a step but offers no explicit context.

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