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JavaScript
Remote

find_cheapest_fuel

Read-onlyIdempotent

Returns the cheapest stations for one fuel grade near a place or coordinate: price per litre, brand, address, distance, open state. Use when the user asks where to fill up or what fuel costs.

Instructions

Returns the cheapest stations for one fuel grade near a place or coordinate: price per litre, brand, address, distance, open state. Use when the user asks where to fill up or what fuel costs. Do NOT use for charging an electric car (call find_charging_station), price history, or traffic (call check_autobahn_traffic). Radius ≤ 25 km, at most 10 stations. For a brand, a name, open now or at a named time, or nearest-first, call find_fuel_station. Each line names the age of its price and opening-hours claim. Prices are consumer information only; the attribution line and MTS-K note must be shown.

Input Schema

NameRequiredDescriptionDefault
latNoLatitude in WGS 84, e.g. 48.137. Use with lon when the caller already holds coordinates; otherwise use place.
lonNoLongitude in WGS 84, e.g. 11.576. Use with lat; otherwise use place.
fuelNoFuel grade: "e5" (Super E5), "e10" (Super E10, the standard German petrol) or "diesel" — LPG/Autogas and CNG are not held by any source here: say so, never substitute a petrol grade. Default "e10". Pass the grade the person named — a diesel driver is not helped by a petrol price.e10
limitNoHow many stations to return, cheapest first (1–10, default 5). The provider's terms cap it at 10.
placeNoWhere to look, as free text: a city ("München", "Munich"), a district or Kreis ("Kreis Fulda"), a Bundesland, a station or stop ("Hamburg Hbf"), a motorway junction ("AK Neufahrn"), or a street address with a house number ("Bahnhofstraße 12, 36037 Fulda"). A motorway number alone ("A7") resolves to the road, which has no single point — name a town or junction on it instead. Use this instead of coordinates whenever the person named a place. An address needs its town or postcode — a street and a number alone exist in many towns. Give either place OR lat+lon, never both.
languageNoSet this on every call to the language the person is writing in: "en" if they wrote English, "de" if they wrote German. Do not leave it out: it defaults to German ("de"), which is only the fallback when the language is genuinely unclear, so an English question sent without it is answered in German — a wrong answer. Place names, station names and road numbers are never translated in either language; in English the German term is kept in parentheses so the person recognises it on signs and in local apps.de
radius_kmNoSearch radius around the place in kilometres (1–25, default 5). The provider's terms cap it at 25 km — a larger circle is a dataset request, not a consumer question.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv2.3.7
    • changedInput schema / properties / fuel / description
      Previous value: -"Fuel grade: \"e5\" (Super E5), \"e10\" (Super E10, the standard German petrol) or \"diesel\". Default \"e10\". Pass the grade the person named — a diesel driver is not helped by a petrol price."New value: +"Fuel grade: \"e5\" (Super E5), \"e10\" (Super E10, the standard German petrol) or \"diesel\" — LPG/Autogas and CNG are not held by any source here: say so, never substitute a petrol grade. Default \"e10\". Pass the grade the person named — a diesel driver is not helped by a petrol price."
  2. Changed1 schema field changedv2.1.18
    • changedInput schema / properties / language / description
      Previous value: -"Set this on every call to the language the person is writing in: \"en\" if they wrote English, \"de\" if they wrote German. Do not leave it out because it has a default — the default is only the fallback when the language is genuinely unclear, and an English question answered in German is a wrong answer. Place names, station names and road numbers are never translated in either language; in English the German term is kept in parentheses so the person recognises it on signs and in local apps."New value: +"Set this on every call to the language the person is writing in: \"en\" if they wrote English, \"de\" if they wrote German. Do not leave it out: it defaults to German (\"de\"), which is only the fallback when the language is genuinely unclear, so an English question sent without it is answered in German — a wrong answer. Place names, station names and road numbers are never translated in either language; in English the German term is kept in parentheses so the person recognises it on signs and in local apps."
  3. Changed1 schema field changedv1.8.29
    • changedInput schema / properties / place / description
      Previous value: -"Where to look, as free text: a city (\"München\", \"Munich\"), a district or Kreis (\"Kreis Fulda\"), a Bundesland, a station or stop (\"Hamburg Hbf\"), a motorway (\"A7\"), or a street address with a house number (\"Hauptstraße 12, 36037 Fulda\"). Use this instead of coordinates whenever the person named a place. An address needs its town or postcode — a street and a number alone exist in many towns. Give either place OR lat+lon, never both."New value: +"Where to look, as free text: a city (\"München\", \"Munich\"), a district or Kreis (\"Kreis Fulda\"), a Bundesland, a station or stop (\"Hamburg Hbf\"), a motorway junction (\"AK Neufahrn\"), or a street address with a house number (\"Bahnhofstraße 12, 36037 Fulda\"). A motorway number alone (\"A7\") resolves to the road, which has no single point — name a town or junction on it instead. Use this instead of coordinates whenever the person named a place. An address needs its town or postcode — a street and a number alone exist in many towns. Give either place OR lat+lon, never both."
  4. Changed1 schema field changedv1.7.3
    • addedInput schema / properties / place / maxLength
      Added value: +120
  5. First observedv0.0.9

TDQS

A4.4/5.0
Behavior4/5

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

Annotations already cover read-only/idempotent/open-world, and the description goes beyond them: provider terms caps (radius ≤ 25 km, ≤ 10 stations), the fact that each result line discloses the age of its price and opening-hours claim, and the mandatory attribution/MTS-K notice. It stops short of describing pagination or result-ordering behaviour beyond "cheapest first", but the added operational and compliance context is substantial.

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?

Purpose and return fields are front-loaded in the first sentence, followed by usage, exclusions, constraints and disclosure requirements. Dense but nearly every clause earns its place; the only slight waste is re-stating the ≤25 km and ≤10 limits already enforced by the schema.

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

Completeness5/5

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

With no output schema, the description compensates by naming the fields returned (price per litre, brand, address, distance, open state) and the legal attribution line. For a 7-parameter, zero-required lookup tool the agent has everything needed to select and invoke it correctly.

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% and each parameter already carries detailed guidance (WGS 84, enum semantics, place-vs-coordinates exclusivity, language default trap). The description restates the radius and count caps but adds no parameter meaning the schema does not already provide, so baseline 3 applies.

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

Purpose5/5

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

Specific verb+resource (returns cheapest fuel stations for one grade near a place/coordinate) with the return fields enumerated. It explicitly distinguishes itself from find_charging_station, check_autobahn_traffic and find_fuel_station, so an agent can route without opening any schema.

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

Usage Guidelines5/5

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

Explicit when-to-use ("where to fill up or what fuel costs") plus explicit when-not-to-use, each paired with the alternative tool to call instead. It also gives the condition that routes to the sibling find_fuel_station (brand, name, open now/at a named time, nearest-first).

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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