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

Annotations already establish read-only, open-world, and idempotent behavior, and the description reinforces these without contradicting them. More importantly, it adds substantial non-obvious behavioral guarantees: 'Unknown items are reported as unknown,' 'never says a link is safe,' 'never probes unrecognized domains,' and 'never suggests a replacement link.' These are high-value behavioral constraints an agent would otherwise have no way to know.

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?

The description is focused and front-loaded with the core action, followed by a compact list of the five evidence points and two boundary statements. It is information-dense with no filler. The five-point list is packed into a long, somewhat run-on sentence, which costs a point, but every clause earns its place and nothing is redundant.

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 read-only inspection tool with an output schema, the description is remarkably complete. It covers what inputs are used for, what the five categories of output are, how unknowns are handled, what the tool will never do, and its side-effect-free nature. Nothing an agent needs to safely invoke this tool is missing, especially given the annotations and output schema supply the remaining structure.

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 description coverage is 0%, placing the burden on the description. It compensates by explaining that the input is an exchange sign-up/referral link (the url parameter) and that country-specific listing and rebate evidence depend on 'a given country' (the optional country parameter). It doesn't spell out formats or defaults, but the semantic role of both parameters is clearly inferable from the five evidence points.

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 starts with a specific verb ('Inspects') and resource ('an exchange sign-up or referral link'), then enumerates five concrete evidence points the tool reports. This makes the tool's function unmistakable and inherently distinguishes it from data-lookup siblings like calculate_trading_cost or get_exchange_fees. It even states what it never does, sharpening the boundary further.

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 description gives clear context: use this tool when you need evidence about a sign-up/referral link's domain, reachability, referral code, country listing, and rebate. It also provides implied exclusions ('never says a link is safe, never probes unrecognized domains, never suggests a replacement link') that tell an agent what not to expect. However, it never explicitly names an alternative sibling such as check_referral_link, so it falls short of fully explicit when-to-use/when-not-to-use guidance.

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