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

With no annotations, the description fully carries the burden of behavioral disclosure. It explicitly states the tool is read-only, lists what it inspects, mentions it returns safe next actions, and explains side effects (leaves registrar and DNS unchanged). It also discloses post-tool implications by noting that transferring preserves nameservers and never migrates DNS implicitly, giving the agent a clear understanding of consequences.

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 contributing unique value. It front-loads the core purpose ('Read-only planner'), then lists inspection targets, outputs, and usage guidance without redundancy. No filler words or repeated information.

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 simple one-parameter tool with no output schema, the description is fully sufficient. It explains what the tool does, what it returns (safe next actions), when to use it, and non-destructive behavior. The context signals show low complexity, and the description fills all necessary gaps, including graceful integration with siblings like get_auth_code.

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 schema has a single parameter 'domain' with a clear description ('Existing domain to inspect, e.g. mysite.com'), achieving 100% schema description coverage. The tool description repeats 'existing domain' but adds no new syntax or format details, so it does not significantly enhance the schema. A baseline of 3 is appropriate because the schema already provides sufficient meaning.

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 is a 'read-only planner for an existing domain' and lists the specific aspects it inspects (registrar, nameservers, DNS provider, DNSSEC, account state, transfer eligibility, price). This distinguishes it from sibling tools like connect_domain or transfer_domain by emphasizing planning and safe next actions.

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 an explicit usage directive: 'Call this before asking for an EPP code,' directly linking it to the pre-transfer workflow. It also clarifies that connecting is free and non-destructive, implying it should be used as a safe first step before any mutating action. This gives clear context and points to an alternative (getting an EPP code).

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