Tankful: Irish heating oil prices

Cheapest heating oil near a place

tankful_county_supplier_prices

Read-onlyIdempotent

Use this when someone asks for the cheapest heating oil or kerosene in an Irish county or Eircode area, which oil supplier is cheapest, how much 300, 500 or 1000 litres costs today, or whether a price they were quoted is fair. Returns named oil suppliers ranked by published delivered price, cents per litre, observation time, the county average and an optional comparison with the quote. Republic of Ireland only. Do not use for Northern Ireland or Great Britain. Reference prices, not quotes or bookable offers.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "location": "<location>"
    },
    "name": "tankful_county_supplier_prices"
  }
}

Input Schema

Name	Required	Description
`litres`	No	Order size. Prices are published for 300, 500 and 1000 litres. For another amount use the nearest size and say so.
`location`	Yes	An Irish county in any common form (Cork, Co. Cork, Corcaigh), a Dublin postal district (Dublin 15, D15), or the first three characters of an Eircode (T12). Do not send a street address.
`quotedTotalEUR`	No	The delivered total in euro, including VAT, that the household was quoted for this order size, to compare with published prices.

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 8, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, non-destructive and closed-world behaviour, and the description adds genuinely new context: results are ranked by delivered price with an observation timestamp and county average, and the data is indicative rather than quotable. It stops short of stating refresh cadence or any limit on how many suppliers are returned, which is the only remaining behavioural gap for a price-lookup tool.

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?

The trigger conditions, the return shape, the geographic limit and the reference-price caveat are packed into four front-loaded sentences with no repetition. Every sentence carries decision-relevant information for an agent.

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 carries the return-value burden itself and does so: named suppliers, ranking, cents per litre, observation time, county average, optional quote comparison. Combined with three fully described parameters and a clear geographic boundary, an agent has everything needed to call 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%, so the parameters are already fully documented and the baseline is 3. The description reinforces the litre tiering (300/500/1000) and explains the purpose of the quote-comparison parameter ('whether a price they were quoted is fair'), but adds no syntax or edge-case detail beyond the schema's own note about using the nearest size.

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?

The description pairs a concrete verb and resource ('cheapest heating oil', 'named oil suppliers ranked by published delivered price') with precise scope: Republic of Ireland counties, Dublin postal districts and Eircode prefixes. It is clearly distinguishable from siblings such as tankful_uk_prices and tankful_business_fuel_prices because it names the geography and audience (households comparing delivered totals).

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?

It enumerates the triggering questions ('which supplier is cheapest', 'how much 300, 500 or 1000 litres costs today', 'whether a price they were quoted is fair') and gives an explicit exclusion: 'Do not use for Northern Ireland or Great Britain'. It also pre-empts a common misuse by stating these are reference prices, not bookable offers.

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

All Tankful: Irish heating oil prices tools Inspect

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