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

Goes well beyond the readOnly/non-destructive annotations by defining the two returned numbers, warning against conflating value with quality score, clarifying domain_score is not confidence/probability, and giving presentation guidance ('NEVER describe domain_score as confidence'). This is exactly the behavioral context an agent needs to interpret results correctly.

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?

Front-loads the purpose, then uses tightly scoped bullets for the two return values and presentation rules. Every sentence adds disambiguation or output-interpretation value; nothing is 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?

Although an output schema exists and would normally remove the need to explain returns, the description still provides critical interpretation guidance that prevents misuse of domain_score. Combined with readOnly annotations and a fully documented single parameter, the definition is complete for correct invocation and presentation.

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?

There is only one parameter and schema description coverage is 100%; the schema already explains that the full domain including extension is required and that any domain works. The description adds no per-parameter syntax or formatting detail beyond what the schema provides, so the baseline of 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 and resource ('Estimate the market value of a domain and explain why'), and the follow-on bullets make clear this is an appraisal tool distinct from lookup/availability/purchase siblings. An agent can identify the tool's function without opening the schema.

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?

Provides explicit triggering conditions ('when a user asks what a domain is worth, how much to pay/offer'), which is strong context. It does not name alternative tools or state when not to use this one versus get_domain_details or check_domain_availability, so it falls short of the 5 bar.

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