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

With readOnlyHint and openWorldHint already present, the description adds meaningful behavior beyond annotations: it explains the x402 payment model, cost per successful call, supported chains, and the important limitation that personal accounts are not exposed. It does not cover rate limits or failure behavior, but the added context is substantive.

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 three tightly written sentences, front-loads the lookup result, then adds the privacy limitation and payment detail. Every sentence contributes useful information without waste.

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 one-parameter read-only lookup with no output schema, the description does enough: it explains what is returned, the personal-account exclusion, and the payment model. Nothing critical is missing for an agent to decide whether and how to call it.

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%, and the single parameter already specifies international digits-only format with an example. The description mentions the phone number concept but adds no syntax or formatting detail beyond the schema, so the schema does the heavy lifting.

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 states a specific verb and resource: checking whether a phone number has a public WhatsApp Business profile and returning business name, photo, and badge. It clearly distinguishes WhatsApp Business data from personal accounts, though it does not explicitly name sibling alternatives such as phone_lookup or osint-phone.

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?

Usage is implied by the WhatsApp Business focus, and the description usefully states that personal accounts are never exposed. However, it does not explicitly say when to choose this tool over general phone lookup siblings or when not to use it beyond the personal-account limitation.

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