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

With no annotations, the description carries the behavioral burden, and it does meaningful work: it states the email-only channel, that a new code is generated and sent, that a Proof account is required, and that authentication must happen before calling. It doesn't mention side effects like invalidating a previous code or rate limits, but the core behavioral traits are disclosed.

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 compact and efficient: two short sentences plus an access note. Every sentence earns its place, and the most important constraints (email-only, new code, authentication prerequisite) are front-loaded with 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 tool with one required parameter and no output schema, the description covers the essential invocation context: what the tool does, which channel it uses, what access is needed, and how to proceed after authentication. It doesn't detail the return value or specify valid sources of the verification ID, but those are either in the schema or inferable from the surrounding flow.

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 schema already documents the single required parameter id as 'Verification ID' with 100% coverage. The description adds no additional parameter-level meaning, so the baseline score of 3 is appropriate.

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: 'Resend a verification message (email channel only)' and explains that it 'Generates and sends a new code.' This clearly distinguishes it from generic login or domain-email flows, but it does not explicitly name sibling resend tools like resend_email_otp, so it falls short of full sibling differentiation.

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 gives concrete usage context: it requires a Proof account, the client must be authenticated first, and it explicitly warns that start_login does NOT open this tool. This provides both a when-to-use condition and a when-not-to-use exclusion, though it doesn't name alternative resend-style tools explicitly.

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