waha_check_number_exists

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the tool checks registration status but does not describe what the check entails (e.g., API calls, rate limits, authentication needs, or response format). For a tool with no annotations, this is a significant gap in transparency about its operation and constraints.

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 that directly states the tool's purpose without unnecessary words. It is front-loaded and efficient, making it easy for an agent to parse quickly. Every word earns its place, achieving optimal conciseness.

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 low complexity (simple check operation), 100% schema coverage, and no output schema, the description is minimally adequate. However, it lacks details on behavioral aspects (e.g., what the check returns or error conditions), which would be helpful for an agent to use it correctly. It meets basic needs but has clear gaps in completeness.

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 description coverage is 100%, so the input schema fully documents both parameters ('phone' and 'session'). The description does not add any additional meaning beyond what the schema provides, such as explaining phone number formats or session context. With high schema coverage, the baseline score of 3 is appropriate, as the description does not compensate but also does not detract.

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: 'Check if a phone number is registered on WhatsApp.' It specifies the verb ('check') and resource ('phone number'), making the function unambiguous. However, it does not explicitly differentiate from sibling tools like 'waha_get_contact' or 'ask_user_via_whatsapp', which might involve similar phone number interactions, so it misses the highest score.

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 no guidance on when to use this tool versus alternatives. For example, it does not clarify if this is for validation before sending messages, how it differs from 'waha_get_contact' (which might retrieve contact details), or any prerequisites like session setup. This lack of context leaves the agent without usage direction.

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