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

Annotations only declare it as non-read-only and non-destructive. The description adds genuinely useful context: a Proof account is required, the client may need authentication, start_login opens a session for this tool, and the call must be repeated afterward. It still omits what happens on success/failure (state transition of the domain, error when no credentials are stored).

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 purpose in the first sentence, then a clearly labeled ACCESS block. Every sentence carries information; the only minor wrinkle is the slightly convoluted phrasing about the session opening the tool.

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 one-parameter mutation with no output schema, the description covers purpose, precondition, and auth flow well. It leaves a gap on return/error behavior and the fallback when credentials are absent, which an agent would benefit from given the dense set of domain-verification siblings.

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% and the single 'id' parameter is fully documented as 'Domain ID to verify'. The description adds no format, source, or lookup guidance for that ID beyond what the schema already says, so the baseline of 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 (verify) and resource (pending domain) and qualifies the mechanism with 'using previously stored DNS credentials', which separates it from the credential-less sibling verify_domain. It stops short of naming that sibling explicitly, so the differentiation is implicit rather than stated.

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?

'Use when credentials are already connected' gives an explicit triggering precondition, and the ACCESS paragraph spells out the authentication prerequisite and the follow-up call pattern. It does not name the alternative path (e.g. verify_domain) or state when this tool should NOT be used.

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