client_isRegisteredUser

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

No annotations are provided, and the description only states the action without disclosing behavior such as whether it performs a network call, what happens for unregistered IDs, or any permission requirements. The description carries the full burden but offers minimal transparency.

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 sentence, directly to the point, with no wasted words. It is well-structured with a clear prefix and 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?

For a simple check operation with two parameters and no output schema, the description is minimally adequate. However, it does not explain the return value or the auto-appending behavior of '@c.us' (though that is in the schema), leaving some context missing.

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 description adds little beyond what is already in the schema. The term 'given ID' loosely maps to the 'number' parameter, but all parameter details are already documented in the schema.

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 uses a specific verb+resource: 'Check if a given ID is registered in WhatsApp'. It clearly distinguishes from sibling tools like client_getNumberId or client_getContactById which retrieve IDs/contacts rather than checking registration status.

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 any prerequisites or scenarios for using this check, nor does it exclude any cases.

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