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

Beyond the annotations, the description explains that the emailed code replaces the texted one, is checked against the email address rather than the phone, and is limited to once per verification. These details make the destructive and non-idempotent behavior concrete.

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 three tight sentences with no filler. The triggering condition is front-loaded, followed by the replacement behavior and the usage limit.

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 destructive mutation with no output schema, the description covers the key behavioral facts an agent needs: replacement of the texted code, email-based proof, one charge, and once-per-verification limit. It does not describe the response or error cases, which is a minor remaining gap.

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%, so the baseline is 3, but the description adds meaningful semantics for the id and email parameters: it clarifies that the same pending verification is reused, that the email address is what the code proves, and that there is one charge. It does not explain the optional user_ip parameter, but the schema already covers it.

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 states a specific action, 'email a new code,' on a specific resource, 'the same pending verification.' It also distinguishes this fallback path from the normal texted-code path by noting that the text did not arrive and that the emailed code replaces the texted one.

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 opening condition 'The text did not arrive' clearly signals when to use this tool, and 'Once per verification' provides an important usage constraint. It does not explicitly name alternatives such as check_verification or send_verification, so it stops short of full when/when-not guidance.

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