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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is fully covered. The description adds only the return shape ("live records grouped by type"), which is modest added value; it says nothing about failure behavior for nonexistent domains, caching, or latency.

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?

Two tight sentences with no waste; the usage trigger is front-loaded ahead of the return description.

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, read-only lookup tool with no output schema, the description covers purpose, when to use it, and the shape of the result. Minor gaps remain around behavior for domains with no records or partial results, but nothing essential to correct invocation is missing.

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% for the single domain_name parameter, including an example (example.com), so the schema does the heavy lifting. The description adds no format or edge-case detail (e.g., subdomain handling) beyond what the schema already provides.

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 (look up) and resource (DNS records for a domain), and enumerates the record types covered (A, AAAA, CNAME, MX, NS, TXT, SOA). This clearly separates it from the narrower siblings mx_lookup, txt_lookup, and cname_lookup, which an agent can distinguish without opening either schema.

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 this when the user wants every DNS record for a domain in one view" gives a clear triggering condition. It does not, however, explicitly exclude the narrower siblings (mx_lookup, txt_lookup, cname_lookup) for single-type queries, so the agent must infer that routing itself.

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