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

With no annotations, the description carries the full burden and does disclose the key non-obvious trait: this is a paid call at $0.003 USDC via x402 on Base, which an agent must know before invoking. It also clarifies that the FX rate is 'current official' with a date and source, implying freshness behavior. It stops short of stating latency, caching, or what happens on unpaid requests.

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?

Two sentences, payload enumerated up front and pricing/access detail relegated to the end — correctly front-loaded. The enumeration is dense but each item tells the agent something it gets, so little is 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?

There is no output schema, so the description must describe return values, and it does so concretely (rates, differential in pp, carry side, FX rate with date/source). The remaining gap is operational: no mention of error behavior, stale-data handling, or how the payment step is triggered.

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 both parameters carry their own descriptions (ISO 4217 or ISO2 country), so the schema does the heavy lifting. The description only refers to 'one currency pair' without adding format, ambiguity, or country-vs-currency resolution guidance, which is the baseline-3 case.

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 names a specific resource ('Carry view of one currency pair') and enumerates exactly what it returns: both policy rates with central bank and last change, the differential in pp, which side earns carry, and the current official FX rate with date and source. That is enough to distinguish it from ranking/convert siblings, though no sibling is named explicitly.

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 implied rather than stated: an agent can infer this is the single-pair drill-down versus carry_ranking (multi-pair) and carry_convert (conversion), but the description never says when to pick this one or names an alternative. No prerequisites or exclusions are given beyond the price.

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