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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds real value beyond them: confirms results are 'real listings only' and describes output shape (price, total with fee, buy URL), plus the fixed-price band ($29–$199).

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 tight sentences, front-loaded with purpose then usage then return/exclusion. No redundancy; every sentence carries distinct 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?

With no output schema, the description still describes the return (price, total with fee, buy URL) and the closed-world constraint, which is the essential missing piece. An agent has enough to call and interpret it correctly.

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 the schema already documents all five parameters with examples. The description reinforces query intent and the $29–$199 range but adds no syntax or format detail beyond the schema; baseline 3 applies.

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 ('search the live 199.domains inventory of brandable and keyword domain names for sale') and scopes it to fixed prices. Clearly distinguishes from get_domain (detail lookup) and list_collections (collection listing) by framing this as the search entry point.

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?

Explains what to pass ('what the person is building', example queries) and adds an exclusion ('never suggests names to register elsewhere'), which sets expectations for this tool's domain. It does not explicitly route to siblings like get_domain for details, but the use context is clear.

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