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

No annotations provided, so the description carries full behavioral burden. It says nothing about what 'check' entails – does it return a boolean, contact info, or a status? No mention of permissions, rate limits, or side effects. 'WhatsApp Web' gives no useful behavioral context.

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?

Two words plus a platform label, but the brevity is under-specification, not efficiency. Nothing is front-loaded or useful.

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 tool with a required parameter, no annotations, no output schema, and 0% schema coverage, the description is completely inadequate. It provides no information an agent needs to call it correctly.

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 0%, and the description adds no information about the 'phone_number' parameter. It doesn't specify format (country code, digits only, E.164), or whether it's the number to check or the checker's number. With one required parameter, the description fails to compensate for the schema gap.

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 'WhatsApp Web: check number' restates the tool name with a platform prefix, adding no specific verb or resource detail. It's essentially a tautology of check_number. It could mean validate, verify registration, or check existence, but none is stated.

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 on when to use this tool, when not to, or which alternatives to consider. Sibling tools are all about messaging and groups, so no clear routing is provided.

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