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

Annotations already establish read-only/idempotent safety; the description adds value by disclosing that the drop window is an estimate, that marketplace parking means 'possibly for sale', and that it points to external alert URLs. This makes the tool's uncertainty and non-authoritative nature transparent beyond the annotations.

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 a compact, front-loaded list with no filler; the opening condition identifies the audience and the colon organizes the data points. The second sentence on alerts is the only add-on, and it earns its place as a distinct feature.

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 nonetheless enumerates the main return categories and the external alert destination, which is sufficient for an agent to decide whether results meet the user's goal. It also states the precondition (taken domain) and avoids promising availability checking.

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 single 'domain' parameter is fully documented in the schema with an example and length constraints, so the description carries little parameter burden. It adds the contextual meaning that the domain is someone else's, but no additional syntax or formatting details.

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 names the exact function: produce options for a domain owned by someone else, and enumerates the returned data (registrar, expiry, lifecycle stage, drop window, marketplaces, backorder links). It clearly distinguishes from availability-checking siblings by framing the domain as taken, so an agent can route correctly.

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 opening phrase 'For a domain someone else owns' gives a clear condition for use: only when the domain is not available. It makes the tool's context obvious, though it does not explicitly name an alternative or state when not to use it.

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