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

Annotations already declare readOnlyHint and openWorldHint=false, so safety is covered; the description adds real value by disclosing what the comparison yields (length, type, words, seller status, value ranges, verdict). It does not cover handling of invalid or unknown domains, which is a minor gap.

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?

A single sentence with no waste: the action and its constraint come first, followed by the exact attributes returned. Every clause earns its place.

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?

For a one-parameter read tool with no output schema, the description adequately previews the return contents so the agent knows what it gets back. Edge-case behavior (nonexistent domains, partial failures) is left unstated but is low risk here.

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 coverage is 100% and the single 'domains' array is fully documented with an example, so baseline is 3. The description does add the 2-to-5 cardinality constraint that is absent from the schema (no minItems/maxItems), which is genuinely useful but not syntax-level detail.

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 (Compare) and resource (.ai domain names) with the exact cardinality (2 to 5) and enumerates the compared attributes. This clearly separates it from single-domain siblings like get_domain or estimate_domain_value without needing 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?

The '2 to 5' bound and 'side by side' framing tell the agent when this tool applies rather than calling estimate_domain_value repeatedly. It stops short of naming an explicit alternative or stating when not to use it, so no exclusions are provided.

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