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

Annotations already declare readOnly/idempotent/non-destructive and openWorldHint=false, so the safety profile is covered. The description adds genuinely non-derivable context: the lists are Real Crypto Signals' compiled regulator warnings, the return fields are named, and the 'empty result does not mean the site is safe' caveat prevents a false-negative interpretation. It stops short of stating list freshness or coverage limits.

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?

Three sentences, zero filler, ordered input → output → interpretation caveat. The most decision-relevant caveat is placed last for emphasis without burying the core purpose.

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 one parameter, a fully documented schema, and no output schema, the description supplies exactly the missing pieces: accepted input formats, the shape of a match, and the critical caveat about empty results. Nothing needed to call or interpret the tool is absent.

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 schema already documents maxLength/minLength/format, so the baseline is 3. The description goes beyond it by giving concrete accepted input shapes ('example-trade.com' or 'https://app.example-trade.com/login'), which resolves the practical ambiguity of whether a scheme or subdomain is needed.

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?

'Look up a website or URL ... in the official regulator warning lists' is a precise verb+resource+scope, and the named example inputs make the target unambiguous against the sibling check_name. It also states what is returned, so the agent knows the resource class and the value of the call before 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?

Usage context is clear: check a site or domain against warning lists, with concrete example inputs showing both bare-domain and full-URL forms. It doesn't explicitly route against siblings such as check_name or latest_warnings, so the when-not-to-use side is inferred rather than stated.

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