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

Annotations already declare readOnlyHint=true, and the description adds genuinely new behavior: what a non-'active' status implies (nameservers not live, records written will not resolve) and what happens when no credential is connected. It does not mention pagination or result-size limits, which is the main remaining gap for a list tool.

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?

Purpose and returned fields are front-loaded, then usage, then caveats — a sensible order with no filler sentences. The trailing 'Read-only.' is redundant with readOnlyHint and slightly inflates the length.

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?

With no output schema, the description usefully enumerates the returned fields (id, status, nameservers) and covers the two failure modes an agent will hit (scoped-away domain, no connected credential). It omits pagination/volume behavior, which is the one thing left unclear for a listing tool.

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 coverage is 100%, so baseline is 3, but the description adds real meaning beyond the schema: 'name' resolves in one lookup rather than a full walk, and credential_name should be omitted unless several credentials exist. The empty-result interpretation is largely duplicated in the schema but reinforces intent.

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 ('List the Cloudflare-hosted domains (zones)') plus scope (limited to what the connected credential can reach) and the returned fields. It also ties itself to the DNS record tools, so an agent can place it in the workflow without opening sibling schemas.

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?

'Call this first to resolve a domain name to the domain_id the DNS record tools take' gives explicit ordering and the alternative path ('pass name' vs walking every domain). It also states the when-not case: if no credential is connected, it reports that and the user must connect one instead.

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