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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It notably states 'Preserves existing records,' which is a key non-destructive trait, along with the Namecheap DNS prerequisite, a token cost, and the HostIds follow-up hint. It doesn't cover error handling or side effects, but for a simple add-record operation this is adequate.

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?

The description is four sentences, each adding distinct value: the core action, a preservation guarantee, a prerequisite, and follow-up/cost info. It is appropriately front-loaded with the primary purpose in the first sentence and contains no redundant 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?

With an output schema present and a fully described input schema, the description only needs to cover what is not already structured: purpose, behavior, prerequisites, and follow-up. This description does all of that effectively, making it complete for this tool's complexity.

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 input schema has 100% parameter description coverage, so the baseline is 3 even without additional param detail in the tool description. The description does not add any parameter-specific context beyond what the schema already provides, so no higher score is warranted.

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?

The description clearly states the tool 'Add one DNS host record to a managed domain without replacing the full zone.' This is a specific verb+resource construction that also distinguishes it from a full-zone replacement operation, which is a likely sibling alternative.

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?

The description provides practical usage context: it contrasts with replacing the full zone, states a prerequisite ('The domain must use Namecheap DNS'), and offers a follow-up action ('Call domains.get_dns_hosts afterward if HostIds are needed'). While it doesn't name a specific alternative tool explicitly, the 'without replacing the full zone' implies a separate path for full-zone edits.

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