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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds real value beyond that: it pre-checks domain ownership and returns a clear error if the domain isn't on the account, which an agent needs to interpret failures correctly.

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 behavior, then examples, then pre-check behavior — good ordering with no filler. The three example queries are slightly redundant with each other but each illustrates a distinct lookup style, so the cost is small.

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 carries return-value burden and does reasonably: it names the record types returned and the error case. It omits response shape/ordering details and doesn't clarify how results differ from lookup_dns, leaving minor gaps for an otherwise simple read 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?

Only one parameter with 100% schema coverage, so the baseline is 4. The description reinforces the ownership constraint ('a domain the customer owns'), matching the schema description without adding contradicting detail.

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 ('Returns the DNS records currently set on a domain') and enumerates record types (A, AAAA, CNAME, MX, TXT, NS) with a concrete analogy ('same data as the registrar's DNS panel'). It doesn't differentiate from the sibling lookup_dns, which is the main gap.

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?

Gives explicit trigger examples ('what's my A record on x.com?', 'show me my MX records'), which directly maps user intent to this tool. It stops short of naming alternatives like lookup_dns or list_my_domains, so the agent must still infer which DNS-related sibling to pick.

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