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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds the legacy status and the availability condition, which is useful context beyond the annotations. It does not describe return format or pagination, but with the annotations covering side effects, a 3 is appropriate.

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 single efficient sentence that includes the tool's purpose, the condition for use, and its legacy status. There is no redundant repetition of the title or schema, and every word contributes to routing the agent correctly.

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?

Given the tool is legacy, the description adequately tells the agent it should normally prefer generateDomainSuggestions. With all parameters documented in the schema and annotations covering safety semantics, the missing output format detail is a minor gap rather than a critical omission. The overall context is sufficient for correct invocation.

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%, with all three parameters fully documented in the input schema. The description adds no parameter-level detail beyond 'domain' being the requested one, and 'limit' and 'sessionKey' are already well explained. Baseline 3 applies because the schema does the heavy lifting.

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 states a specific action ('Suggest alternative domain names') and the triggering condition ('if the requested one is unavailable'). It also explicitly distinguishes this from generateDomainSuggestions by marking it as legacy, so an agent can tell what this tool does and how it relates to its sibling.

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 description gives explicit routing guidance: 'Legacy; prefer generateDomainSuggestions.' This tells the agent not to choose this tool when generateDomainSuggestions is available. While it doesn't list every possible alternative, it names the exact sibling that should be used instead, which is sufficient for correct selection.

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