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

Annotations declare readOnly and openWorld but carry no cost, scope, or charging behaviour, and the description adds all three: $0.002 USDC per successful call via x402 with failed calls not charged, plus a summary of what a hit returns (port, online status, family, country, AS, first/last seen). It omits rate limits or latency, but it substantially expands what the structured fields provide.

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?

The description is front-loaded with the core operation, then that a hit's fields follow, then scope limits, then pricing. Each sentence earns its place, though the return-field enumeration is partly redundant with the output schema.

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?

A single-parameter lookup with an output schema and read-only annotations is well covered: what it checks, what it returns, what it does not cover, and what it costs. Nothing needed to invoke the tool correctly is missing.

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?

One parameter with 100% schema description coverage, so the schema already says the input must be an IPv4 address with an example. The description mentions 'IPv4 address' but adds no format, normalization, or edge-case guidance (e.g. private ranges, IPv6). Baseline 3.

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: checking an IPv4 address against the abuse.ch Feodo Tracker C2 blocklist, with named malware families (Emotet, QakBot). The scope caveat 'Covers only the C2 servers this feed tracks' helps distinguish it from generic IP-reputation siblings, though no sibling is named by name.

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?

The coverage statement gives a clear usage boundary: this answers questions about C2 infrastructure for known feeds, not general IP reputation. It does not explicitly point to alternatives such as security_abuseipdb_check or security_talos_ip_blacklist, but the context for when it applies is clear.

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