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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true, so 'Read-only' is largely redundant. 'Cannot spend money' does add real value in a namespace where quote_domain, set_budget, and get_finance exist, since it rules out cost exposure. What is missing is behavior for a batch scan: partial-failure handling per candidate, latency, or rate limits across up to 25 lookups.

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 short sentences, zero waste. The scope and the 25-item cap are front-loaded, and the differentiator and the safety clause follow in descending order of importance.

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?

No output schema exists, and the description carries the return-value burden well by listing the six classification fields produced per domain. The 25-item cap and read-only/no-cost guarantees round it out. It stops short of describing the response shape (per-candidate objects vs. errors) for a batch call, which is the one remaining gap.

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?

Only one parameter and schema description coverage is 100%, so the schema already specifies 'Full domain names, max 25.' The description reinforces the 25 cap but adds no syntax guidance (bare domain vs URL, subdomain handling, deduplication) beyond the structured field. 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 (classifies) and resource (an explicit list of up to 25 domains) and enumerates what is produced: registered, resolves, serves, parked, classification and liveness. The clause 'for when the user already has specific names rather than a concept' distinguishes it from the concept-driven siblings (suggest_names, recommend_name), though it doesn't distinguish it from per-domain siblings like audit_domain or check_live.

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?

There is a usable usage cue: use this when the user already has specific names rather than a concept. That is enough to imply the boundary against name-generation tools, but nothing explains why an agent should pick this over audit_domain, check_live, quote_domain, or verify_ownership for the same names, which is the harder routing decision.

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