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

No annotations exist, so the description carries the full behavioral burden. It does disclose a real-world side effect (an SMS is actually sent), but omits operational traits an agent needs: OTP expiry, whether a new code invalidates a prior one, rate limits, and whether sending incurs credit cost given the presence of check_credits and count_sms_parts siblings.

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?

A single sentence that is front-loaded with the core action and free of filler. It is tight and readable, though it could have used its spare room for the missing behavioral detail.

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?

Both required parameters are fully documented and there is no output schema to explain, so the tool is callable as-is. However, for a send-with-side-effect tool with zero annotations, the absence of expiry, cost, and verification-flow context leaves real gaps.

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%, with both 'to' (with an example format) and 'sender' documented in the schema itself. The description adds nothing beyond that, so the baseline 3 is appropriate for a schema that does the heavy lifting.

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: generates and sends an OTP code via SMS for user authentication. This clearly distinguishes it from the generic sibling send_sms and from verify_otp (which checks a code). It never explicitly names those siblings, but the purpose is 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 authentication framing implies when to use it, but there is no explicit when/when-not guidance and no mention of the natural pairing with verify_otp or the point at which a code should be re-generated. Usage must be inferred rather than read.

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