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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint=false), and the description adds genuinely new operational context: the check flags lookalikes, typosquats, brand names in unofficial domains and newly registered domains, spans roughly 130 tax authorities and 11 African countries, and carries a per-call cost of $0.005 USDC via x402 on Base mainnet. That pricing and authentication detail is exactly the kind of behavior an agent needs before deciding to call a paid endpoint.

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?

It is effectively one long but well-ordered sentence that leads with the core purpose and then layers scope, detection capabilities and pricing. The brand examples (SARS, KRA, M-Pesa) are repeated between the title and the description, which is mild redundancy, but nothing is padded or wasted.

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?

For a one-parameter read-only lookup the description covers scope and cost well, but with no output schema it never describes what a call actually returns — a verdict, a confidence flag, the matched official domain, or a list of anomalies — which leaves the agent unable to anticipate the response. Country coverage is also fuzzed as 'South Africa and 10 other African countries', so the boundary of applicability is only approximate.

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?

There is a single required parameter and schema description coverage is 100%, so the schema already defines `url` and supplies examples. The description restates that it accepts a link or domain but adds no format constraints, normalization rules, or handling of bare domains versus full URLs beyond what the schema shows, 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?

The description states a specific verb and resource — a phishing URL and fake-website check that compares a link or domain against official domain lists — and enumerates the covered sectors and regions. It does not, however, distinguish itself from the sibling domain_intel, whose name suggests overlapping domain-reputation functionality, so an agent cannot fully rule out the alternative from the text alone.

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?

Usage is only implied: the tool is clearly framed as a link-safety check for African banking, tax and mobile-money domains, so an agent can infer the right call context. There is no explicit when-not-to-use statement, no mention of when to prefer domain_intel, and no guidance on what to do with the verdict.

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