Resolves real-time global foreign exchange fiat rates ($0.0005 USDC)
| Name | Required | Description | Default |
|---|---|---|---|
| baseCurrency | No | Base currency ticker symbol (default USD) | USD |
| Name | Required | Description | Default |
|---|---|---|---|
| base | No | Base currency ticker | |
| rates | Yes | Key-value pair of fiat rates | |
| success | Yes | Query status |
Changes observed during successful MCP inspections.
Input schema / properties / baseCurrency / descriptionAdded value: +"Base currency ticker symbol (default USD)"Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "base": {
+ "description": "Base currency ticker",
+ "type": "string"
+ },
+ "rates": {
+ "description": "Key-value pair of fiat rates",
+ "type": "object"
+ },
+ "success": {
+ "description": "Query status",
+ "type": "boolean"
+ }
+ },
+ "required": [
+ "success",
+ "rates"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=false, and destructiveHint=false, so the safety and idempotency profile is covered. The description adds a pricing detail ($0.0005 USDC), which is useful behavioral context, but does not describe latency, data source, rate limits, or error behavior.
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 with the core purpose front-loaded and no filler. The cost annotation is the only extra and it earns its place by informing invocation cost.
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 one-parameter read-only oracle with an output schema and rich annotations, the description covers purpose and cost adequately. It does not need to explain return values because an output schema exists, though it could mention base-currency behavior or data freshness.
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%, and the single baseCurrency parameter is fully documented in the schema with its default. The description adds no parameter meaning beyond the schema, so the baseline of 3 applies.
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 ('Resolves') and resource ('real-time global foreign exchange fiat rates'), clearly distinguishing this oracle from siblings like weather_oracle or arc_network_oracle_query. The parenthetical cost is incidental but the core purpose is unambiguous.
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 no when-to-use guidance, no alternatives, and no conditions for selecting this tool over other oracle/data-feed siblings. Usage is only implied by the name and resource phrase, so the agent must infer context.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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