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

No annotations are present, so the description carries the burden. It discloses the check-only nature, the Proof-account requirement, and that a session/login may be needed before the call succeeds. It could explicitly state that no DNS changes are made, but 'Check if...' and the pre-verification framing already imply a read-only operation.

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 short and front-loaded, with purpose first, then usage, then access. The auth sentence is slightly convoluted ('a session opens this tool') and contains client-specific guidance, but every sentence contributes information and there is no redundancy.

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 tool with no output schema, the description covers what the tool does, when to call it, and the prerequisite authentication, which is enough to invoke it correctly. The main minor gap is that it does not describe what the returned result looks like beyond implying 'confirm the credentials work.'

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 describes the only parameter (`id`: 'Domain ID to check credentials for') at 100% coverage. The description adds little about parameter semantics beyond connecting the domain to stored credentials, so the high-schema-coverage 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?

The first sentence states a specific verb and resource: 'Check if stored DNS credentials have access to a domain.' It is not a tautology, and the phrase 'before triggering verification' distinguishes this preflight check from verification/check siblings such as verify_domain or check_domain_verification.

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?

It gives explicit when-to-use context: 'Use before triggering verification to confirm the credentials work.' It also spells out the authentication prerequisite and retry flow (start_login, then call again). It does not name the exact alternative tools or say when not to use it, so it does not earn a 5.

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