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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The one genuinely additive fact is the billing model ('Cost: $0.25 USDC via x402'), which tells the agent this is a paid call with an auth/payment requirement. Beyond that it says nothing about rate limits, failure modes, or whether results are cached.

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 capability and output list, then use cases, then cost. Every sentence carries distinct information — no restatement of the tool name or filler.

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?

With no output schema, the description correctly carries the return-field burden by enumerating the eight result categories. Combined with full schema coverage and annotations, an agent has enough to call it correctly. It omits pricing/error handling nuance and any hint of response structure, which keeps it from a 5.

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%: 'lookup' is documented as an IPv4/IPv6 address with an example, and 'language' is documented with its enum and default. The description only reconfirms that both IPv4 and IPv6 are accepted; it adds no format or edge-case guidance beyond the schema. 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 ('IP address intelligence' for any IPv4 or IPv6 address) and enumerates exactly what comes back: geolocation, ASN, organization, CIDR, hostname, abuse contact, reputation. No sibling tool covers IP profiling, so the resource boundary is unambiguous even within a large family of '*_profile' tools.

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?

Names four concrete use cases (fraud detection, security investigations, traffic analysis, visitor identification), which gives an agent clear positive routing signals. It stops short of stating when not to use it or naming an alternative for overlapping needs such as email trust or company verification.

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