Submit up to 1,000 phone numbers for asynchronous WhatsApp validation. Deducts 1 WA credit PER NUMBER upfront (the whole batch is rejected if the balance is insufficient), so confirm quantities before submitting large batches. Returns a batch_id immediately with status "processing" — retrieve results with whatsapp_batch_status.
| Name | Required | Description | Default |
|---|---|---|---|
| phone_numbers | Yes | Phone numbers to validate (duplicates are removed automatically). Max 1,000. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true) by disclosing the cost model (1 WA credit per number, deducted upfront), the all-or-nothing failure mode when balance is insufficient, and the immediate return shape (batch_id with status "processing"). These are exactly the side effects an agent must know before invoking.
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 tight sentences, front-loaded with capability then cost then return/next-step. Every sentence carries distinct, actionable information 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?
No output schema exists, yet the description covers the return value (batch_id, "processing" status) and the follow-up tool, plus the billing consequence. An agent has everything needed to call and continue the workflow 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 coverage is 100% and the single parameter already documents the 1,000 max and automatic duplicate removal, so the description's restatement of the limit adds little. Baseline 3 is appropriate when the schema carries the parameter burden.
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 (submit), resource (phone numbers), and scope (up to 1,000, asynchronous WhatsApp validation), which cleanly separates it from the single-number sibling check_whatsapp and from the retrieval sibling whatsapp_batch_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?
Explicitly routes the agent to whatsapp_batch_status for retrieving results, and the credit warning frames when to be careful with large batches. It stops short of saying when to prefer a single-number check over a batch, so usage context is clear but not fully exhaustive.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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