Send an OTP

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

Annotations already indicate it's a write operation (readOnlyHint=false) and non-destructive (destructiveHint=false). The description adds crucial behavioral context: it deducts from wallet balance, attaches an idempotency key, and returns a reference UUID for tracking. These details go beyond annotations and help the agent understand side effects.

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 four sentences, front-loading the critical cost implication ('Deducts from your wallet balance'). Every sentence adds value: cost, core functionality, return reference and tracking, idempotency, and required scope. No redundant or unnecessary text.

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?

Given 5 optional parameters and no output schema, the description covers the return value and idempotency but omits details like default OTP length, channel behavior when both email and mobile are absent, or that the OTP should be verified via hellio_verify_otp. The openWorldHint allows some leeway, but for a payment-incurring tool, more completeness is expected.

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?

The input schema has 100% description coverage, so the baseline is 3. The description does not elaborate on parameter usage beyond what the schema provides. It mentions the reference return value but does not add parameter-specific constraints or relationships (e.g., required combinations of email and mobile_number). The description adds no new parameter semantics.

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 clearly states it generates a one-time passcode and delivers it via SMS, voice, or email, deducting from wallet. The title 'Send an OTP' and the mention of 'otp scope' distinguish it from generic messaging tools like hellio_send_sms. The verb 'send' and resource 'OTP' are specific and unambiguous.

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 mentions the required 'otp' scope and that the reference can be tracked with hellio_get_message, implying a use case for OTP delivery. However, it does not explicitly state when to use this tool over alternatives like hellio_send_sms or hellio_send_voice, nor does it mention the complementary tool hellio_verify_otp. Usage guidance is implied but not direct.

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