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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description's only added behavioral context is "Spends nothing," a cost signal not present in the structured fields, which is genuinely useful. It says nothing about pagination behavior or result size, though the schema covers those.

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?

Two short sentences with no padding, but the first is a sentence fragment and the second ("Spends nothing") is cryptic out of context. It is brief without being well-formed or front-loaded with a clear action.

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 simple, fully annotated, read-only paginated list tool with 100% schema coverage and no output schema, the description plus structured fields give an agent enough to call it correctly. The only real omission is explicit sibling routing, which is a minor gap at this complexity level.

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 page, rows, and cluster each documented in the schema itself, including the pointer to total_pages and the source of cluster ids. The description adds no meaning beyond that, so the baseline of 3 applies.

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 phrase "A page of the domains in one cluster" names the resource and the paginated scope, but omits a verb (list/get), so it reads as a noun phrase rather than a statement of what the tool does. An agent can infer it retrieves domains belonging to a cluster, and the title reinforces this, but it is not distinguished from siblings like extract_from_cluster or list_clusters.

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?

There is no guidance on when to use this tool versus siblings such as list_clusters, extract_from_cluster, or search. "Spends nothing" implies it is a free/cheap operation, which is a hint, but no explicit when-to-use or when-not-to-use condition is given.

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