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

Goes well past the annotations by disclosing the cost model ($0.002 USDC per successful call via x402 on Base/Solana/Arc, failed calls free) — critical for an agent deciding whether to spend. It also discloses the return fields (phish id, verification flag, validity) and the important interpretation limit that absence of a record is not a safety verdict.

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?

Four sentences, all informative and front-loaded with the purpose before the return semantics and pricing. Slightly dense, but no sentence is filler — the pricing clause in particular earns its place for an agent managing spend.

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?

Covers everything an agent needs to invoke correctly: input constraint, what is returned, how to read a null result, and the payment requirement. The output schema exists, so the return-value sentence is redundant but harmless; nothing material 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?

Only one parameter and schema coverage is 100%, so the schema already fully documents the required URL. The description repeats the 'http or https' constraint already present in the parameter description, adding no new syntax, normalization, or format guidance. 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 (look one http/https URL up in PhishTank) plus the exact lookup mechanism ('live checkurl lookup'). Naming the specific threat-intel source implicitly separates it from sibling feeds like security_openphish_feed or security_urlhaus_malware, so an agent can pick it without opening the 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?

'Looks one http or https URL up' plus 'no key' makes the single-URL, keyless use case clear, and the absence caveat tells the agent how to interpret a negative result. It stops short of naming alternatives (bulk feed tools such as security_openphish_feed or domain-level checks like security_surbl_uri_lookup) as explicit substitutes.

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