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

Beyond the read-only annotations, the description reveals plan-dependent behavior (DLR only on Enterprise plans), return field semantics (`is_active`, `expires_at`, `DLR`), and even decodes failure reasons like `failed.Undeliverable` and `failed.Provider`. This is rich behavioral context that annotations alone do not provide.

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 sentences, each earning its place: the first states the core function, the second details plan-dependent outputs with actionable failure semantics, and the third gives the use case and points to the correct alternative. The most important information is front-loaded, and there is no filler.

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-parameter, read-only tool with an output schema, the description fully covers what an agent needs: purpose, plan differences, failure meaning, and a clear distinction from the verification tool. The output schema handles return structure, so the description's omission of field types is appropriate.

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%, and the schema already thoroughly documents `message_id` as 'The UUID returned by `generate_otp` — this identifies which OTP you want a status report on.' The description adds no further parameter-specific detail, so the 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?

The description opens with a specific verb and resource: 'Check whether a previously sent OTP is still active and ... get its delivery status.' It clearly differentiates itself from the sibling `verify_otp` by explicitly stating 'Does NOT verify a code; use `verify_otp` for that.' This leaves no ambiguity about the tool's role.

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 concrete use case: 'Useful when an end user reports they didn't receive the code — you can confirm whether MyOTP delivered it before deciding to resend.' It also names the alternative tool for code verification, providing both a when-to-use and when-not-to-use directive.

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