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

Annotations already carry the read-only safety profile, and the description adds substantial behavioral context beyond that: fresh appraisals can take up to a minute (latency), repeat lookups within 48 hours are cached and instant (caching/rate-limit relevant), and the reply must include report_url. It also discloses what the result contains (market value in dollars plus supporting signals).

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 sentences, each earning its place: what it does and returns, when to use it, and the latency/caching/report_url behavior. Purpose is front-loaded and there is zero 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?

With one fully-documented parameter, no output schema, and a read-only annotation, the description carries the full burden of explaining the return value — and it does: estimated market value in dollars with the signals behind it, plus the report_url handling. Nothing an agent needs to invoke it correctly is missing.

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 baseline is 3. The description adds no extra meaning about the domain parameter beyond what the schema already provides (e.g., no format caveats or edge-case guidance), but it doesn't need to since the schema fully documents the single parameter.

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: "Estimate what a domain name is worth" — clear this is a valuation tool, not a domain-info tool. The listed signals (comparable sales, marketplace listings, appraisal model, SEO data) make it easily distinguishable from the sibling get_domain_info without needing to open either 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?

Gives explicit when-to-use conditions: "when the user asks what a domain is worth, whether one is a good buy, or to compare domain values." This is clear context, but it never names or excludes the closest alternative (get_domain_info), so it stops short of full when-not/alternative guidance.

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