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

Annotations already declare this is a non-readonly, non-idempotent, open-world mutation, and the description adds real context beyond them: that it dispatches an SMS with a 6-digit code and is the first half of a two-step verification flow. It does not disclose re-send behavior, code expiry, or any rate limits, which would be the remaining useful details.

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 that front-load the precondition and action. Each sentence carries weight, though the closing line about the pro knowing them is more rationale than instruction.

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-param tool with no output schema, the description conveys the workflow, trigger, and next step adequately. The main gap is phone-number format, which neither the description nor the empty schema resolves.

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?

With one parameter at 0% schema coverage, the description must carry the semantics. It only implies the phone value is a mobile number via 'their mobile number' and gives no format guidance (E.164, country code, punctuation). This is marginally better than the bare schema but leaves the parameter under-specified.

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 action (text a 6-digit code to a mobile number) tied to a clear precondition (before a client's first booking). It also distinguishes itself from its sibling confirm_my_phone, which handles the code read-back, so an agent can route between the two without opening either 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?

It gives a clear trigger ('before a client's first booking') and names the follow-up tool confirm_my_phone for the next step. It stops short of an explicit when-not case (e.g., don't call if the number is already verified), so it isn't fully exhaustive.

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