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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, so the write/charge profile is partly covered structurally. The description does add genuine context beyond that: the fee is billed monthly from the rate sheet via the wallet with credit used first, and that the response omits the submitted digits. It still does not say what happens on an incorrect or expired code, which matters for a confirmable, charged mutation.

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 action and the confirm semantics are front-loaded and the sentences are short with no repetition of the title. The closing line 'The same on every client' is filler with no actionable meaning, and 'The answer leaves the digits out' is an awkward way to say the response redacts the code.

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?

With no output schema, the description usefully covers the return-value behavior (digits omitted) plus billing and preview semantics, which is the right load-bearing content for a 3-parameter charged mutation. The remaining gap is error/retry behavior and the purpose of did_id.

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 67%; the description mostly restates what the schema already documents (code is 4 to 8 digits, confirm false is a charge-free preview) without adding format or validation detail. The one parameter with no schema description at all, did_id, is never mentioned in the description, leaving that gap unaddressed.

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 opens with a specific verb and resource: submits the WhatsApp registration code, and clarifies the code is the one the person received by text or call. That implicitly sequences it after the request-code step, but it never names whatsapp_number_request_code as the sibling that produces the input, so sibling differentiation is left to inference.

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?

It states the prerequisite source of the code (the text or the call) and explains the two modes: confirm false is a preview that sends nothing and charges nothing, versus a real submission. It stops short of any explicit when-not guidance, such as what to do if no code has been requested or the code is wrong.

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