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

No annotations exist, so the description carries the full behavioral burden and does so well: non-destructive add semantics, the exact 409 conflict condition, and the escape hatch via a sub-label. It stops short of mentioning auth/permission requirements, propagation timing, or the response payload, so it is strong but not exhaustive.

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 dense sentences, each front-loading the actionable constraint: what to add, which type for which content, and the conflict behavior with fix. No filler and nothing repeated from the schema.

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 annotations and no output schema, the description closes the important gaps: mutation scope, unique-conflict error semantics, and alternatives. An agent can call this correctly and handle the main failure mode without further context.

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%, so the schema already documents all five parameters — baseline 3. The description adds genuine meaning by mapping type values to expected content (A/AAAA→IP, CNAME→hostname, TXT→verification string) and clarifying the 'host' sub-label hostname distinction, which goes beyond the schema text.

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 ('Add a DNS record to a subdomain you already own') with enough scope detail to separate it from delete_record, remove_forward, and remove_proxy. The record-type enumeration (A/AAAA/CNAME/TXT) further pins the tool's identity.

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?

Explicitly tells the agent when each record type applies, that adding does not replace existing records, when the call is refused (409 while the label carries a forward or proxy), and the two remediation paths (remove_forward/remove_proxy first, or use 'host' for a different hostname). This is textbook routing guidance.

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