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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description goes beyond that by disclosing that a country value activates CoinRebate's availability records for that country and by enumerating exactly which referral artefacts are returned, which the annotations cannot convey. It stops short of mentioning data 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?

The negative guidance is front-loaded, which is the right priority for an agent deciding whether to call it, and the return-value sentence is dense with useful content. The prose is somewhat long and the closing 'use it only for...' sentence partially restates the scope already implied by the negative list.

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 an output schema present the description does not need to spell out return shape, and with annotations covering safety it does not need to restate read-only behaviour. What remains — scope, exclusions, the effect of the optional country parameter, and the boundary against order/advice requests — is fully covered.

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%, so the baseline is 3. The description nonetheless adds meaning the schema lacks: the schema merely says 'for compliance check', while the description explains that passing country applies CoinRebate's stored availability records for that country. The exchange param adds no semantics beyond the schema's enumerated exchange names, so it is not a full 5.

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 precise verb and resource (look up a referral code, fee discount and signup link for one exchange) and enumerates the exact returned fields including maker/taker fees before and after discount. This distinguishes it from siblings like get_exchange_fees, compare_fees and check_referral_link, which do not combine referral data with per-exchange fee tables.

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?

It gives an unusually explicit when-not list (investment advice, order placement, exchange sign-in, moving funds) and a positive scope rule ('use it only for questions about an exchange referral code, signup link or fee discount'). The only gap is that it never names a sibling tool as the alternative for the excluded cases, so the routing is stated by task rather than by target tool.

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