Check multiple phone numbers for WhatsApp accounts in one read-only request and get registration status plus user JID. Supply numbers with country code, digits only.
Check many phone numbers at once for WhatsApp accounts. Read-only. Pass numbers with country code, digits only. Returns whether each number is registered, with its user JID.
| Name | Required | Description | Default |
|---|---|---|---|
| phones | Yes | List of phone numbers to check |
Changes observed during successful MCP inspections.
v2.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnlyHint, openWorldHint), and the description reinforces it with 'Read-only' while adding genuinely useful input-format constraints ('country code, digits only') and return shape ('registered, with its user JID'). It does not cover rate limits or batching limits, but it adds real behavioral context beyond the annotations.
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?
Three short sentences, front-loaded with purpose, then format, then return value. Every sentence earns its place with no filler.
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 single-parameter read tool, the description covers purpose, input format, and return value; annotations carry the safety profile. Nothing an agent needs to call it correctly is 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 coverage is 100% and there is only one parameter, so the baseline is already high. The description goes beyond the schema's generic 'List of phone numbers' by specifying the required format (country code, digits only), which is meaningful guidance an agent needs to invoke correctly.
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?
States a specific verb and resource ('Check many phone numbers at once for WhatsApp accounts') and the batch scope immediately distinguishes it from the single-number sibling whatsapp_check_user. An agent knows exactly what it does without opening the schema.
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 phrase 'many phone numbers at once' clearly implies the batch use case versus the singular check tool, giving a solid selection signal. It stops short of explicitly naming whatsapp_check_user as the alternative or stating exclusions, so it is clear context rather than full routing guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.