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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), so the bar is lower, and the description nevertheless adds substantive behavior: default exclusion of expired names, where expired names live (chain history), the paging contract, and an untrusted-data warning. It does not mention rate limits or result-size behavior beyond pagination, keeping it off 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?

Ordering and scope are front-loaded, then default behavior, then pagination, then the trust caveat – a sensible priority sequence with no filler sentences. The trailing untrusted-name note is slightly jargon-heavy but is security-relevant, so it earns its place.

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?

An output schema exists, so return fields need not be restated, and the description still explains the paging outcome contract (next_after/exhausted). Combined with full schema coverage and annotations, an agent has essentially everything needed to call it correctly; only explicit sibling routing is absent.

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%, so the schema already documents all four parameters, making 3 the baseline. The description reinforces include_expired semantics (active-only default) and cursor reuse ('pass next_after from the previous result unchanged'), which is helpful but largely duplicates the schema text.

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 (List) and resource (names) with a scoping qualifier (start with a prefix) plus the result ordering ('shorter names first, then byte order'), which separates it from exact-match siblings like lookup_name. It never names an alternative tool explicitly, so it stops short of a 5.

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?

Implies usage through the include_expired toggle and the paging loop instruction ('Page through large results with next_after until exhausted is true'), which is genuinely actionable context. However there is no explicit when-to-use/when-not statement or routing to siblings such as lookup_name or get_name_history.

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