OpenVan MCP Server

Find Cheapest Fuel

find_cheapest_fuel

Read-onlyIdempotent

Rank countries by fuel price in a region or worldwide, ascending or descending, to find lower-priced fuel and plan routes.

Instructions

Rank countries by the price of a fuel type in a region (or worldwide): the cheapest first, or with order=most_expensive the most expensive first. Useful for route planning. Use it for «where is fuel cheapest» and, with order=most_expensive, «where is fuel the most expensive», in a region or worldwide.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`limit`	No	How many countries to return.
`order`	No	cheapest first (default) or most_expensive first — «where is fuel the most expensive».	cheapest
`locale`	No	Language the user writes in (en, ru, de, fr, es, pt, tr). Set it on every call: the answer and the interactive card are shown in this language and units; without it the card falls back to the app's interface language.
`region`	No	Region to search. Default: world (all countries).	world
`fuel_type`	No	Fuel type. e.g. gasoline, diesel, lpg, cng, e85.	diesel

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedv0.6.4Oct 15, 2026

changedInput schema / properties / fuel_type / description

Previous value: -"Fuel type. Uses the same keys as /api/fuel/prices prices."New value: +"Fuel type. e.g. gasoline, diesel, lpg, cng, e85."

changedInput schema / properties / limit / description

Previous value: -"How many cheapest countries to return."New value: +"How many countries to return."

addedInput schema / properties / locale

Added value: +{
+  "description": "Language the user writes in (en, ru, de, fr, es, pt, tr). Set it on every call: the answer and the interactive card are shown in this language and units; without it the card falls back to the app's interface language.",
+  "enum": [
+    "en",
+    "ru",
+    "de",
+    "fr",
+    "es",
+    "pt",
+    "tr"
+  ],
+  "type": "string"
+}

addedInput schema / properties / order

Added value: +{
+  "default": "cheapest",
+  "description": "cheapest first (default) or most_expensive first — «where is fuel the most expensive».",
+  "enum": [
+    "cheapest",
+    "most_expensive"
+  ],
+  "type": "string"
+}

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": true,
+  "properties": {},
+  "type": "object"
+}

First observedv0.6.0Oct 3, 2026

TDQS

A3.6/5.0

Behavior3/5

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

Annotations already declare read-only, idempotent, open-world, and non-destructive behavior. The description restates ordering and scope but adds little behavioral context beyond the schema, such as rate limits, caching, or output format (output schema exists).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the core ranking action and order behavior, but repeats 'order=most_expensive' and 'region or worldwide' across clauses, adding mild redundancy. Still compact and readable.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Covers purpose, usage context, and ordering. With a rich schema, output schema, and annotations handling safety and returns, the definition is nearly complete for an agent; it omits only a note on locale/language effect, which the schema covers.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all five parameters are fully documented in the schema. The description only restates the order and region parameters without adding syntax, defaults, or usage nuance beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Rank countries') and resource (fuel price by region), with the ordering behavior. It is clear what the tool does, though it does not explicitly differentiate itself from siblings like compare_fuel_prices or get_fuel_prices.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides clear context: useful for route planning and for answering 'where is fuel cheapest/most expensive' in a region or worldwide. It does not mention when not to use it or name alternative tools, so it stops short of a 5.

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