dns_lookup

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

No annotations are provided, so the description carries the burden, and 'using the system resolver' is a genuine behavioral disclosure — it tells the agent results reflect local resolver config (hosts file, configured DNS), not authoritative DNS. However, it says nothing about failure behavior (NXDOMAIN vs error), timeouts, or whether both A and AAAA records are returned.

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?

One short sentence, front-loaded with the verb and free of filler. It is arguably slightly under-specified rather than bloated, which is the right kind of brevity failure.

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?

An output schema exists, so return values need not be described. But for a network-dependent tool with no annotations and an undocumented parameter, the description should at least flag error behavior and record-type scope; neither is present.

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 single 'host' parameter has 0% schema description coverage, so the description must compensate; calling it a 'hostname' clarifies that a name rather than an IP literal is expected. It still omits format expectations (FQDN vs short name, trailing dot, scheme rejection), leaving the one parameter only partially specified.

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?

Specific verb ('Resolve') plus resource ('hostname') and the outcome ('its addresses'), so an agent knows exactly what the call produces. It does not explicitly distinguish itself from nearby network siblings like check_tcp_port or http_request, which is the only thing keeping it from a 5.

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?

There is no statement of when to use this versus alternatives such as web_fetch or http_request, and no mention of prerequisites like whether the hostname must be fully qualified or whether the host must be reachable. The usage is only implied by the verb.

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