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

With no annotations, the description carries the entire behavioral burden. It does not disclose whether a successful verification consumes the code, whether failures are counted/rate-limited, or what a success/failure response looks like – all material for a security-sensitive verification action.

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 front-loaded sentence with zero waste and the key scope term "previously sent" early. Efficient, though its terseness borders on under-specification for a tool with no annotations.

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 simple 3-param OTP tool the purpose is clear and parameters are fully documented in the schema. However, with no annotations and no output schema, the description leaves return-value shape and error/consumption behavior entirely unexplained.

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%, so the schema already explains code, phone, and site_url in detail. The description adds no meaning beyond what the schema states, so baseline 3 applies.

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 ("Verify") and resource ("OTP") with scope ("previously sent"), which cleanly distinguishes it from the sibling send_otp. It stops short of naming send_otp or get_otp_usage explicitly, so true sibling differentiation is only implied.

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?

"previously sent" implies a prior send_otp call is required, so the basic context is implied. But there is no guidance on when to use this versus get_otp_usage, nor on exclusions, prerequisites, or failure cases, leaving usage to inference.

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