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

Annotations already declare readOnly, openWorld=false and idempotent, so the safety profile is covered; the description still adds useful behavior: no arguments, no external calls, and the fact that live-fetched sources never appear in this listing. It stops short of saying how often dataset state changes or how to refresh, but the marginal value over the annotations is real.

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 purpose, then usage, then behavior in three tight paragraphs with no filler. The parenthetical dataset enumeration is long, but it is the one piece of content that tells an agent what coverage to expect, so it largely earns its space.

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 values need no explanation, and the annotations carry the safety/idempotency profile. For a zero-argument inventory tool the description covers purpose, the decision context, the exclusion set, and the no-side-effects guarantee — nothing an agent needs to invoke it correctly 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?

The tool takes zero parameters, which is the baseline-4 case, and the description confirms this explicitly ('takes no arguments'), removing any question of whether filtering arguments are available. There is nothing further to document.

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 the local datasets and feeds behind lookup_target') and enumerates the dataset families covered (RIR, IANA, PSL, cloud/CDN, Tor/Private Relay, reputation, GeoLite2). It also returns concrete fields (state, record count, generation date, stale flag), so an agent can distinguish this inventory tool from lookup_target immediately.

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 states when to use it ('judge how current a reputation, RIR, cloud or geolocation answer is', 'explain why such a section is missing') and draws a clear exclusion boundary: registry, DNS and Web3 data are fetched live and are not listed here. Both the trigger and the non-coverage are spelled out.

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