navi_usd_fx_rates

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

No annotations are provided, so the description carries full burden. It discloses update frequency ('updated daily'), output contents ('rate of 1 USD against every supported currency plus the last-update timestamp'), authentication ('No API key required'), and pricing ('$0.002 USDC per call'). This is rich behavioral context.

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, each earning its place: the first states the core function, the second gives the use case, the third explains the output and cost. Front-loaded with the most important information, no redundancy.

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?

Given the tool's low complexity (0 params, no output schema), the description is complete: it covers what the tool does, what it returns, how often it updates, authentication, and cost. There are no glaring gaps.

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?

The tool has zero parameters and the schema description covers 100% of the schema (empty object with a note that no parameters are needed). Baseline for 0 params is 4, and the description reinforces that no parameters are required, adding no confusion.

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?

States a specific verb and resource: 'Real-time USD exchange rates to 160+ currencies.' Clearly distinguishes itself from siblings like navi_crypto_prices by focusing on fiat FX rates, not crypto.

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?

Provides clear context for when to use: 'Useful for AI agents that pay in USDC and need to convert or display prices in other currencies.' Does not explicitly name alternatives or exclusions, but the use case is well-defined.

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