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

Goes well beyond the readOnly/openWorld annotations: it discloses the response contents (listed yes/no, every return code with its meaning, lookup link), that the answer is point-in-time, and a precise cost model — $0.002 USDC per successful call via x402 on Base/Solana/Arc, with failed calls uncharged. Payment/auth requirements and cost are exactly the kind of context annotations don't carry.

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?

Front-loads the core action and list coverage, then appends result shape and pricing; every clause carries information. It is dense, but the heavy parenthetical list is justified by the scope it defines.

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?

Everything an agent needs to invoke correctly is present: input choice, what returns, cost, and freshness semantics. An output schema exists, so return-value detail need not be expanded further.

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 both parameters already document their formats and test entries (127.0.0.2, dbltest.com). The description adds the semantic mapping of ip→ZEN and domain→DBL, but no further syntax or validation detail, so it lands at the baseline.

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 (blocklist check) and resource (Spamhaus ZEN / DBL) and enumerates exactly what each zone covers (SBL, CSS, XBL, DROP, PBL vs DBL). An agent can distinguish this from neighboring reputation tools purely from the description.

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?

Clearly frames the two usage modes — IPv4 address against ZEN, domain against DBL — and notes the result is a point-in-time answer, which tells the agent not to treat it as a live monitor. It does not explicitly name alternatives (e.g. abuseipdb, spameatingmonkey, surbl) or say when not to use it, so it stops short of the top score.

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