OpenVan MCP Server

Compare Fuel Prices

compare_fuel_prices

Read-onlyIdempotent

Compare current fuel prices for one fuel type across 2-10 countries and return a cheapest-first table so users can see which named country has cheaper fuel.

Instructions

Compare current prices for one fuel type across 2-10 countries. Returns sorted table cheapest-first. Use it when someone asks which of two or more named countries has cheaper or more expensive fuel.

Input Schema

Name	Required	Description	Default
`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.
`fuel_type`	No	Fuel type to compare. e.g. gasoline, diesel, lpg, cng, e85.	diesel
`country_codes`	Yes	Array of 2-10 ISO 3166-1 alpha-2 country codes to compare.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.9.7Oct 25, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```
- changedOutput schema / additionalProperties
```
Previous value: -trueNew value: +{}
```

Changed3 schema fields changedv0.6.4Oct 15, 2026

changedInput schema / properties / fuel_type / description

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

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"
+}

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

A4/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is settled. The description contributes beyond that by disclosing the return ordering (sorted cheapest-first), which meaningfully changes how an agent presents results.

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

Conciseness5/5

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

Three short sentences with zero filler: capability and scope first, return shape second, usage trigger third. Every sentence carries information an agent needs.

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?

An output schema exists, so return values need no explanation, and the annotations cover safety semantics. What remains uncovered is edge behavior with unrecognized or unsupported country codes; a brief note on that would close the gap.

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 country_codes bounds, the fuel_type enum with its diesel default, and the locale enum are already fully documented in structured fields. The description only restates the count range and single-fuel-type scoping, adding no new syntax or edge-case meaning.

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 and resource (compare fuel prices) and scopes it precisely: one fuel type across 2-10 countries. This implicitly separates it from get_fuel_prices (single country) and find_cheapest_fuel, though neither sibling is named explicitly.

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?

Gives an explicit trigger condition: use when someone asks which of two or more named countries has cheaper or more expensive fuel. It does not state when NOT to use it (e.g., a single country query should go to get_fuel_prices), so an agent must infer the exclusion from the 2-10 country constraint.

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