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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior, so the bar is lower. The description adds real behavioral context beyond them: the signal is a 'narrow list-based' lookup with inherent false-negative risk, IPv4-mapped IPv6 is routed to the IPv4 list, and responses carry list date and attribution.

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?

Three sentences, front-loaded with the core action and scope, then the caveat about the signal's limits. The IPv4-mapped IPv6 parenthetical duplicates the schema text and is the only mildly wasteful element in an otherwise dense, well-ordered description.

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?

The tool is simple (one required param, no nested objects) and the annotations cover the safety profile, so the description needs little more. It partially compensates for the absent output schema by noting that list date and attribution are included, though it does not say what a positive match actually returns (categories, matched netblock, etc.).

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?

With a single parameter at 100% schema description coverage, the schema already carries the full semantics, and the description largely restates it (including the same IPv4-mapped IPv6 parenthetical). It adds no new syntax, normalization, or edge-case detail beyond the schema, so the baseline 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?

Specific verb ('Checks') plus resource ('IPv4 or IPv6 address') and the exact nature of the data source ('curated list of netblocks known to be hijacked or run by spam/cyber-crime operations'). It is far more precise than a tautology, but it never names or contrasts the close sibling 'address_risk' or 'url_reputation', so an agent still has to guess which reputation tool is the right one.

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?

Usage is implied by the resource type, and the description usefully warns that 'a clean result is not a safety guarantee', which shapes interpretation of results. However, it gives no explicit when-to-use condition, no prerequisites, and does not route the agent to or away from alternatives such as address_risk for related address-risk questions.

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