start_domain_email_verification

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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false), and the description adds real behavioral context beyond them: it discloses the side effect of dispatching a code to a standard admin mailbox and the authentication precondition (API key or active session). It stops short of saying whether this can be re-invoked, how codes expire, or how to complete verification.

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 action and its effect are front-loaded in the first sentence, and the ACCESS block is clearly segmented rather than buried in prose. It is appropriately sized for a two-parameter tool, with only mild redundancy between the title-level phrasing and the body.

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 small, enum-bearing tool with no output schema and full schema coverage, the description covers the action and the auth gate adequately. It omits the natural next step (confirming the emailed code, e.g. via confirm_domain_email_code) and any note on code lifetime, which an agent orchestrating the flow would want.

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 documents both 'id' and the enumerated 'email_prefix' with its default. The description only loosely echoes the email-prefix concept ('standard admin email address') without adding format or constraint detail, so the baseline 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?

States a specific verb and resource ('Start domain verification via corporate email') and adds what actually happens ('sends a verification code to a standard admin email address at the domain'). This is clear, though it does not distinguish itself from close siblings like start_domain_verification or setup_domain_email, so an agent cannot fully rule out the alternatives from the description alone.

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 useful prerequisite guidance (needs a Proof account, PROOF_API_KEY, or a session opened via start_login), which tells the agent when it is callable. It does not, however, say when to choose this over the many related siblings such as start_domain_verification or setup_domain_email, so the selection guidance is only implied.

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