find_cheapest_fuelFind the cheapest countries for a given fuel type in a region (or worldwide). Useful for route planning.
| Name | Required | Description | Default |
|---|---|---|---|
| limit | No | How many cheapest countries to return. | |
| region | No | Region to search. Default: world (all countries). | world |
| fuel_type | No | Fuel type. Uses the same keys as /api/fuel/prices prices. | diesel |
Changes observed during successful MCP inspections.
Input schema / properties / fuel_type / descriptionPrevious value: -"Fuel type."New value: +"Fuel type. Uses the same keys as /api/fuel/prices prices."Input schema / properties / fuel_type / enumPrevious value: -[
- "gasoline",
- "diesel",
- "lpg",
- "cng"
-]New value: +[
+ "gasoline_regular",
+ "gasoline",
+ "gasoline_premium",
+ "gasoline_super",
+ "diesel_regular",
+ "diesel",
+ "diesel_premium",
+ "lpg",
+ "cng",
+ "e85",
+ "kerosene",
+ "premium"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds a purpose hint (route planning) but nothing about how 'cheapest' is ranked, data freshness, or what the country results contain. With annotations doing the heavy lifting, a 3 is appropriate.
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 efficient sentence with the core action front-loaded and the parenthetical scope qualifier appended. No waste, though it is arguably terse for a tool with 3 parameters and an enum of 12 fuel keys.
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?
A read-only query that needs no output schema, and annotations cover the safety profile; schema coverage is complete for all three params. The only minor gap is that it does not describe what the 'cheapest countries' result contains (country names, prices, ranking).
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 both enums are documented in the schema, so the baseline is 3. The description only restates the region/fuel-type intent in prose ('a given fuel type in a region (or worldwide)') without adding limits, defaults, or key syntax beyond the schema.
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 (find) and resource (cheapest countries for a fuel type in a region), plus scope qualifiers (region or worldwide). It is clearly distinguishable from siblings like get_fuel_prices and compare_fuel_prices, though it never names them explicitly.
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 only usage hint is 'Useful for route planning', which is vague and does not explain when to pick this over the sibling fuel tools (get_fuel_prices, compare_fuel_prices). No prerequisites, exclusions, or alternative conditions are given.
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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