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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so safety is covered structurally. The description adds real value beyond that by explaining the null `live_url` semantics and how the agent should respond to it, though it says nothing about result volume or ordering for larger accounts.

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?

Five short sentences, each earning its place: purpose, return fields, the `url` guarantee, the `live_url` null case with a prescribed action, and the sibling pointer. The most decision-relevant constraints are front-loaded.

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 no parameters, no nested objects, and no output schema, the description carries the return-shape burden itself and does so by listing the key fields plus the one field whose null value changes agent behavior. Nothing needed to call or interpret 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?

The tool takes zero parameters, so there is no parameter semantics to document and the baseline of 4 applies. The description correctly devotes its space to return-value semantics instead.

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 ('List all websites owned by the current user') and enumerates what comes back (subdomain, publish status, plan tier, creation date, URLs). It explicitly differentiates from the sibling get_site by scoping itself to listing and pointing to get_site for per-site detail.

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?

Names the alternative ('Use get_site for per-site detail') and gives concrete handling guidance: share `url` because it always resolves, and when `live_url` is null offer publish instead of a link. The when-to-use and the edge-case behavior are both explicit.

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