oegb-kraken-mcp

Get tariff rates or standing charges

get_tariff_rates

Read-onlyIdempotent

Retrieve unit rates or standing charges for a specified Octopus Energy tariff, including half-hourly Agile prices, and filter results by date period.

Instructions

Get unit rates or standing charges for a tariff, e.g. half-hourly Agile prices. Public. Prices are in pence, with value_exc_vat and value_inc_vat. Use day-unit-rates / night-unit-rates only for Economy 7 (E-2R-...) tariffs. Results are newest first. Narrow with period_from / period_to.

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": {
      "product_code": "<product_code>",
      "tariff_code": "<tariff_code>",
      "fuel": "<fuel>",
      "rate_type": "<rate_type>"
    },
    "name": "get_tariff_rates"
  }
}

Input Schema

Name	Required	Description
`fuel`	Yes
`page`	No	Page number for paginated results (use next_page from the previous call).
`page_size`	No	Results per page (default 100, max 1500).
`period_to`	No	ISO 8601 datetime, ideally with a Z or offset, e.g. 2026-01-01T00:00:00Z. Without a timezone, Europe/London is assumed.
`rate_type`	Yes
`period_from`	No	ISO 8601 datetime, ideally with a Z or offset, e.g. 2026-01-01T00:00:00Z. Without a timezone, Europe/London is assumed.
`tariff_code`	Yes	e.g. E-1R-AGILE-FLEX-22-11-25-C
`product_code`	Yes	e.g. AGILE-FLEX-22-11-25

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Nov 10, 2026

TDQS

A3.8/5.0

Behavior3/5

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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so safety is covered. The description adds useful context beyond that: the endpoint is public (no auth), prices are in pence, and results come back newest first. It does not discuss rate limits, page limits, or failure modes, so it adds moderate rather than rich context.

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?

Five short sentences, each carrying distinct information, with the core purpose front-loaded. Sentence fragments like "Public." are terse to the point of feeling clipped, but nothing is redundant.

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?

For an 8-parameter tool with no output schema, the description compensates by disclosing the key return fields (value_exc_vat, value_inc_vat) and units. Pagination is left entirely to the schema, and differences in shape between unit-rate and standing-charge responses are not covered, keeping it from a 5.

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

Parameters4/5

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

With 75% schema coverage the schema carries most parameter documentation, but the description still adds meaning: the Economy 7 constraint on rate_type and the narrowing purpose of period_from / period_to beyond their ISO-8601 format description. Ordering behavior (newest first) is also implied as fixed, which matters for the period filters.

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?

Names a specific verb and resource ("Get unit rates or standing charges for a tariff") and gives a concrete example domain (half-hourly Agile prices). It is clearly distinguishable from siblings like get_consumption or list_products, though it never explicitly contrasts itself with them.

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 a real exclusion rule: day-unit-rates / night-unit-rates only apply to Economy 7 E-2R-... tariffs. It also tells the agent to narrow with period_from / period_to. It stops short of naming an alternative tool for related needs, so not a 5.

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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