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

With no annotations, the description carries the full burden and does state 'Read-only' plus the default record set returned, which is genuine behavioral context. It says nothing about failure modes (NXDOMAIN, timeout), rate limits, or whether the lookup hits authoritative or resolver caches.

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?

Three short clauses, front-loaded with the action, then the default return set, then the narrowing option and safety note. Every sentence earns its place with no filler.

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 two-parameter read tool with no output schema, the description covers what is returned and how to narrow it, which is the key missing piece an agent needs. It stops short of describing error output or response shape, but is otherwise adequate.

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% and both parameters are documented with examples and a default, so the schema does the heavy lifting. The description only restates the 'types' narrowing behavior and the default set, adding no syntax or format detail beyond the schema.

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?

Names a specific verb (Resolve) and resource (DNS records for a host name) and enumerates the default record set, so the agent knows exactly what it gets back. It does not explicitly distinguish itself from close siblings such as mx_lookup, reverse_dns or dns_propagation, which keeps it short of 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?

Usage is only implied: it is the general-purpose DNS resolver, and 'pass types to narrow' hints at the narrowing workflow but never says when to prefer mx_lookup or another sibling instead. No when-not conditions or prerequisites are given.

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