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

No annotations are provided, so the description must disclose behavior on its own. It discloses that the operation creates a verification record and returns instructions, which implies a state change, but it does not mention side effects (e.g., whether an email is sent), idempotency, failure modes (e.g., domain already verified), or any destructive potential. The access note is useful but does not cover behavioral traits.

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 brief and front-loads the core purpose in the first sentence. The second sentence adds a necessary access instructionants, though slightly verbose with the parenthetical. No redundant information is included.

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?

The description conveys the basic action and access requirement, and the schema covers parameters. However, it does not explain the B2B domain context, how this tool relates to numerous domain-verification siblings, what the returned instructions look like (no output schema), or what might happen if prerequisites (like an existing domain) are not met. For a moderately straightforward tool, this is adequate but not fully complete.

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 all three parameters (domain, customer_id, verification_method) are already described in the input schema. The tool description adds no additional meaning or examples beyond the schema, 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 clearly states the action ('Start a B2B domain verification') and the outcome ('Creates a verification record and returns DNS/HTTP instructions'). The B2B qualifier hints at a distinction from user-level verification, but it does not explicitly name or contrast any sibling tool, so it falls short of full 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 provides an authentication prerequisite (needs a Proof account, authenticate via /mcp) and a cryptic warning that 'start_login does NOT open this tool.' However, it gives no guidance on when to use this tool versus alternatives like start_user_domain_verification or check_domain_verification. No when-to-use, no exclusions of siblings.

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