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

Annotations already declare non-readOnly, idempotent, non-destructive, open-world. The description adds real behavioral context beyond that: other domains redirect visitors and search engines, only one copy is indexed, and the target domain must already be live. It doesn't describe reversibility or the response, keeping it from a 5.

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 tight sentences with no filler, and the core action is front-loaded ahead of the redirect consequence and the usage condition. Every sentence earns its place, though it is slightly longer than strictly necessary.

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 mutation with no output schema, the description covers the effect, the redirect/indexing consequence, the liveness prerequisite, and the selection context. Only return/confirmation behavior is left unaddressed, which is minor 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 parameter is fully documented in the schema ('exactly as it was connected'). The description adds the liveness prerequisite, which is meaningful, but otherwise the schema carries the semantics. Baseline 3 is appropriate.

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: making one connected domain a site's main address. It also distinguishes from siblings by referencing check_domain for the liveness prerequisite, so an agent can tell this apart from add_domain/list_domains without opening a 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?

Explicitly gives the when-to-use condition ('a site has more than one domain and the person says which should be the main one') and names the check_domain prerequisite. It lacks an explicit when-not-to-use, but the usage context is clear.

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