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

readOnlyHint=true already declares safety, so the description correctly spends its words on semantics instead: wordpress is null for code services, heldDomains covers bought names pointing at no service. These are interpretive rules an agent cannot derive from annotations alone; it stops short of noting ordering or size limits.

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?

Front-loaded with the scope, then the field list, then the heldDomains and wordpress caveats, then the entry-point note. The field enumeration is dense but each clause carries meaning; it is a long sentence-chain rather than tight prose.

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 an output schema present, return values are already structured, so the description need only orient the agent — which it does via the entry-point framing and the wordpress/heldDomains edge cases. Some of the field list duplicates the output schema, but nothing an agent needs to call 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?

Zero parameters, so there is nothing to disambiguate and the baseline of 4 applies. The description correctly spends no space on input arguments.

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?

Opens with a specific verb+resource and scope: "Every service on this account", then enumerates the concrete fields returned. It is unmistakably distinct from siblings like list_plans, list_dns or list_backups, which each target a narrower resource.

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 starting point of a session" tells the agent to call this first and explains that its ids feed every other call's serviceId/domainId. That is strong when-to-use guidance, though it doesn't explicitly name an alternative for cases like looking up a single service.

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