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

With no annotations, the description alone must disclose behavior. It only says 'live rates across currencies' and gives no information about response format, whether data is real-time or delayed, authentication requirements, or default behavior when parameters are omitted. This is minimal disclosure.

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 short (8 words), but it is redundant: 'Fx Snapshot' in the description repeats the tool name and is followed by 'Forex snapshot,' essentially saying the same thing twice. The remaining clause 'live rates across currencies' is useful but could be stated more efficiently.

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?

The tool has no output schema and no annotations, so the description needs to explain what the tool returns and how parameters behave. It does not describe the return structure, whether results are for a single base or all currencies, or what happens when base/targets are omitted. This is incomplete for an agent to invoke it confidently.

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 description coverage is 100%, so the baseline is 3. The schema descriptions ('Base to process', 'Targets to process') are vague placeholders, but the tool description's mention of 'currencies' adds some context implying base and targets are currencies. Still, no format, examples, or required/optional semantics are clarified.

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 clear resource: 'Forex snapshot — live rates across currencies,' indicating the tool returns current forex rates. It is more specific than a vague label, but it does not explicitly differentiate itself from sibling tools like x402-forex or x402-currency-rate.

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?

No guidance is provided about when to use this tool versus alternatives such as x402-currency-convert, x402-forex, or x402-currency-rate. The description does not mention scenarios, exclusions, or which sibling tool to choose for other needs.

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