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

Given annotations already declare readOnlyHint=true and idempotentHint=true, the description adds valuable behavioral context: sorting order (OPTIMAL → ADVERSE), the inclusion of stability tiers and regulatory flags, and the 'Free' cost note. This exceeds what the annotations alone provide.

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 three sentences, each serving a distinct purpose: what it returns, how it's sorted, and when to use it. It is front-loaded with the core function and contains no redundant or filler content.

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 simple read-only list tool with a single optional parameter and an existing output schema, the description covers all essential aspects: scope, data fields, ordering, use case, parameter usage, and cost. Nothing critical is missing.

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 for the single 'from' parameter is 100%, with the schema already explaining it as an optional filter. The description repeats this ('Filter by source currency with the from parameter') without adding new semantic detail, so it meets the baseline but doesn't elevate it.

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 clearly states the tool returns all 60+ currency corridors with stability tier, volatility, and regulatory flags. The phrase 'compare corridors before choosing a payment route' distinguishes it from sibling tools like fx.rate or stability.corridor, which likely focus on single values or specific corridors.

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 explicitly says 'Use to compare corridors before choosing a payment route' and provides a concrete example. It doesn't name alternative tools or mention when not to use it, but the context is clear enough for an agent to infer the appropriate scenario.

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