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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds real context beyond that: the external data source (HackerTarget) and the fact that results reflect what 'the resolver holds' — i.e. possibly cached/stale records rather than authoritative truth. It omits auth/rate-limit behavior for the third-party endpoint.

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-loads the colloquial invocation phrasings first, then the technical capability, then the use case — good ordering with no filler. The three quoted query examples are slightly redundant for an agent but serve intent-matching, so minor waste only.

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, no-output-schema tool this is nearly complete: capability, source, returned record types and use contexts are all present. Missing only edge behavior such as NXDOMAIN handling or whether results are cached, which is a minor gap.

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% and the schema already carries the 'hostname, not a URL — strip scheme and path' guidance, so the description adds no parameter meaning beyond structured data. Baseline 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+resource (forward DNS lookup via HackerTarget) and enumerates the record types returned (A/AAAA/MX/NS/SOA). This distinguishes it cleanly from siblings like reverse_dns, as_lookup, and dns_host_search, which an agent can rule out immediately.

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 clear usage contexts: checking where a domain currently points and confirming a DNS change has propagated. It does not explicitly name the sibling to prefer for reverse lookups or host-history searches, so the routing guidance is implied rather than exhaustive.

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