x402_fx

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

With no annotations provided, the description carries the full burden. It does add useful behavioral context—per-call cost and the full-table mode—but it does not disclose what happens when both parameters are omitted, error behavior, or any rate-limit/auth concerns.

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?

A single sentence packs in the operation, the key usage exception, and the cost, all front-loaded with no filler. Every element earns its place.

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 two-parameter, read-like converter, the description covers the core call pattern, the table mode, and cost. It does not describe the response shape or the behavior when both arguments are absent, but those are minor given the tool's simplicity and the absence of an output schema.

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 adds meaning beyond the schema by explaining that omitting 'to' triggers the full-table response, which the schema's optional-parameter declaration does not convey.

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 concrete operation—currency conversion—rather than repeating the tool name. The added 'omit to for the full table' hint clarifies scope, though it does not explicitly differentiate from siblings like x402_crypto or x402_stock.

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 implies the use case (when currency conversion is needed) and gives one specific usage rule: omit 'to' to get the full table. However, it names no alternatives and provides no exclusions or conditions for when not to use the tool.

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