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

Annotations only declare readOnly and openWorld; the description adds real behavioral context: what the verdict contains, that risk_reason is available on every plan while the full signal breakdown requires Pro and up, and that each call consumes one monthly quota lookup. That plan gating and billing detail is exactly the kind of information annotations cannot express.

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?

One front-loaded sentence that opens with the verdict and then layers in result contents, plan tiering, and quota cost. It is dense but every clause carries information; the nested parenthetical '(Pro plan and up)' is the only mildly awkward structural element.

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?

There is no output schema, so the description must describe the return values, and it does so thoroughly: score range, band, label, reason, per-signal points and source, and the specific VPN/proxy/Tor/datacenter/hijacked/bot flags. Combined with the quota and plan notes, an agent has everything needed to call this correctly.

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 coverage is 100% and the single `ip` parameter is already documented as 'A public IPv4 or IPv6 address.' The description restates the public-address and single-address constraint but adds no format, syntax, or edge-case guidance 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?

States a specific verb and resource ('Risk verdict for ONE public IP address') and enumerates exactly what is returned (risk score, band, label, reason, breakdown, flags). The 'ONE' emphasis tells an agent this is the single-address tool, distinguishing it from bulk_lookup without naming it.

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 rather than stated: 'ONE public IP address' rules out batch use and the quota sentence signals a metered lookup. However, it never explicitly says when to pick this over lookup_ip or bulk_lookup, nor does it state exclusions such as private or reserved addresses.

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