Send Phone Verification Code

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

Goes well beyond the annotations: discloses the 10-minute re-send throttle returning codeAlreadySent, the 5-per-day cap, and the PHONE_VERIFY_UNAVAILABLE country restriction. Annotations only say non-idempotent/non-destructive; the description supplies the operational limits that actually govern calling behavior.

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?

Purpose and the VERIFICATION_REQUIRED trigger are front-loaded, and every following sentence carries a distinct constraint (fallback, throttle, geo limit, guide). It is dense but the clauses are all load-bearing; only minor tightening is possible.

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 compensates by naming the error outcomes (codeAlreadySent, PHONE_VERIFY_UNAVAILABLE) and linking a guide. For a one-parameter, non-idempotent action tool, an agent has everything needed to call it and handle the response.

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 already defines the channel enum, so the baseline is 3. The description adds genuine value by explaining the reason to switch to channel: "call" (SMS didn't arrive, have the code read out), which is semantic guidance the enum alone does not convey.

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+resource (send a phone verification code) and immediately ties it to the concrete condition it resolves (VERIFICATION_REQUIRED), which cleanly separates it from confirm_phone_verification and the top-up/registration siblings.

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 says when to use it (clear VERIFICATION_REQUIRED for purchases/top-ups), what it cannot do (number is fixed, not choosable), the follow-up step (ask user, then call confirm_phone_verification), and the fallback (retry with channel: call). Alternatives and exclusions are named, not inferred.

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