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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), and the description adds genuinely non-obvious behavior: a $0.002 USDC charge per successful call via x402 on Base/Solana/Arc, with failed calls not billed. That billing detail materially affects invocation strategy (e.g. avoid speculative calls). It stops short of mentioning rate limits, latency, or coverage gaps in the feed.

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?

Two tight sentences with the purpose front-loaded and the price note last. The field list is dense but scannable, and nothing is 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 an output schema present, the description needn't restate return values, and it covers purpose, data sources and cost. The only gaps are invocation-relevant edge cases: input normalization and whether 'not found' versus 'known malicious' is distinguishable in the response.

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 'host' parameter is already documented as 'Domain or IPv4 address, e.g. 221.15.252.30', so the schema does the heavy lifting. The description adds no extra semantics such as hostname normalization, subdomain handling, or behavior for malformed input, 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?

Names a specific verb ('Checks whether') and a specific resource/feed ('abuse.ch URLhaus as a malware distribution host'), then enumerates exactly what evidence is returned. An agent can distinguish this from siblings like security_phishtank_check, security_threatfox_iocs or security_spamhaus_zen without opening any schema.

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 malware-hosting use case is made clear, so an agent can infer when the tool applies, but there is no explicit when-to-use guidance, no prerequisites, and no routing to alternatives (e.g. PhishTank for phishing URLs, ThreatFox for broader IOCs, Spamhaus ZEN for IP reputation). Usage is implied rather than stated.

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