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

With no annotations supplied, the description carries the full behavioral burden and does so well: it explains null semantics for hidden/absent `about` and `profile_picture_url`, notes picture URL expiry, defines the `unavailable` field for unreadable parts, and specifies the 404 `not_registered` error for numbers without WhatsApp along with the 3-credit billing cost.

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?

Nearly every clause earns its place — field list, null rules, error case, group, billing — and the key purpose is front-loaded. The opening sentence is a heavily nested run-on that is harder to parse than it needs to be, costing a point on structure.

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?

There is no output schema, so the description must describe the return shape, and it does so thoroughly by naming the fields, their nesting (businessProfile sub-fields), and their null/error behavior. An agent has everything needed to call this correctly and interpret the result.

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% on a single `phone` parameter, so the schema already documents format, accepted variants (spaces, dashes, `00` prefix, `14155550123@c.us` form) and an example. The description adds nothing about the parameter, so the baseline 3 applies.

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: retrieving everything WhatsApp exposes about the account behind a phone number, and enumerates the returned facets (pushname, isBusiness, verifiedName, businessProfile, about, picture URL, LID, device count). This is clearly distinguishable from the sibling check/search/channel tools, which deal with registration status, channels, and groups rather than a number's profile.

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 description implies usage (fetch profile metadata for a known WhatsApp number) and the `not_registered` 404 tells the agent what happens for a non-account, but it never states when to prefer this over `get_v1_number_check` or any other sibling, and there are no explicit exclusions or prerequisites.

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