start_user_domain_verification

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

Annotations only declare readOnlyHint=false and destructiveHint=false, so the description carries real weight and does so: it explains the required account, the PROOF_API_KEY vs start_login paths, and the odd detail that a session can open this tool, requiring a re-call. It still omits what state gets created and how to progress afterward (e.g., check_user_domain_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?

Front-loaded with the core action, then a clearly separated ACCESS block. Both sentences earn their place, though the second sentence is dense and slightly awkward with the em-dash construction.

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 two-parameter tool with no output schema, the description covers authentication but not the follow-up path. In a namespace crowded with domain-verification siblings, it should direct the agent to the status-check tool (check_user_domain_verification) and would benefit from distinguishing 'user' verification from the other start_* verification tools.

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 both parameters (domain, channel enum dns/http) are already documented in the schema. The description echoes the DNS/HTTP distinction but adds no format, default, or constraint detail beyond what the schema already provides. 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?

States a specific verb and resource: 'Start a self-service domain verification session.' It also names the mechanism (DNS or HTTP challenge). However, it does not distinguish itself from closely named siblings like start_domain_verification, start_domain_email_verification, or start_domain_email_verification, which an agent could easily confuse it with.

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 context ('user proves ownership of a domain') and covers the auth prerequisite ('needs a Proof account ... sign in with start_login'), which is genuinely useful. It does not say when to prefer this over the similarly named start_domain_verification sibling, so usage routing is only implied.

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