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

With no annotations, the description carries the full burden. It discloses that the tool returns an array of records and includes record types and cost, which adds useful context. However, it does not mention error behavior, rate limits, or prerequisites (e.g., domain ownership), leaving some behavioral opacity.

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 brief and front-loaded with the core purpose, then details output format and optional parameter. Every sentence is informative, including the token cost. No filler or redundancy.

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 straightforward read tool, the description covers the purpose, output shape, optional filtering, and cost. An output schema exists, so return values are further documented. It lacks explicit guidance on when to avoid this tool, but overall it is sufficient.

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%, so parameters are already well-defined. The description adds value with a subdomain example but does not introduce new semantics beyond the schema. Baseline 3 is appropriate.

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 opens with a specific verb and resource: 'Fetch DNS records for a domain.' It clearly distinguishes this tool from sibling domain tools like whois, rdap, and lookup. The scope (records under a domain) is explicit.

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 explains the optional subdomain parameter and gives a concrete example (blog.example.com). However, it does not state when to choose this tool over alternatives such as domains.whois or domains.lookup, and no exclusions or alternative suggestions are provided.

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