Apier MCP Server

Norges Bank exchange rate

get_exchange_rate

Read-onlyIdempotent

Fetch Norges Bank exchange rates for any currency against NOK, the official benchmark for Norwegian tax and accounting obligations. Returns the rate and valid date, with fallback to prior business day.

Instructions

Fetch the most recent Norges Bank exchange-rate reference for a currency against NOK — the canonical conversion benchmark Norwegian tax + accounting authorities accept for obligations in foreign currency (Årsregnskap, cross-border MVA, dividend reporting). The currency-of-record lookup; takes no Norwegian-company input. Returns the rate, the date it is valid for (weekday rates only; weekends / holidays return the prior business day's rate), and source attribution. Input: { base, quote, date? } — ISO 4217 codes, NOK-ANCHORED: exactly one side MUST be 'NOK'. A pair without a NOK side is rejected client-side as UNSUPPORTED_CURRENCY_PAIR — fetch both NOK legs and derive the cross rate yourself. Failure modes: VALIDATION_FAILED, UNSUPPORTED_CURRENCY_PAIR, INVALID_DATE, UPSTREAM_TIMEOUT, NO_RATE_AVAILABLE, SCOPE_INSUFFICIENT (needs read:norgesbank). For compliance obligations or filing deadlines rather than a currency rate, use get_company_summary instead. Docs: https://www.apier.no/docs/mcp

Input Schema

TableJSON Schema

Name	Required	Description
`base`	Yes	Base currency — ISO 4217 three-letter code (case-insensitive). Exactly one of base/quote must be 'NOK'.
`date`	No	Optional ISO 8601 date (YYYY-MM-DD); omit for the latest published rate. Non-business days fall back to the prior business day.
`quote`	Yes	Quote currency — ISO 4217 three-letter code (case-insensitive). Exactly one of base/quote must be 'NOK'.

Output Schema

TableJSON Schema

Name	Required	Description
`_meta`	No
`result`	Yes	The Norges Bank NOK reference rate, the date it is valid for, and the source attribution.
`metadata`	Yes
`justification`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.2.1Sep 26, 2026

TDQS

A5/5.0

Behavior5/5

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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description discloses key behaviors: returns the rate with its valid date, weekday-only rates with prior business day fallback, client-side rejection for unsupported pairs, and a full list of failure modes. This significantly enriches operational understanding without contradicting the annotations.

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 description is front-loaded with the core purpose, then efficiently presents usage constraints, failure modes, and an alternative tool reference. Each sentence carries operational value, and the length is justified by the domain complexity; no filler or redundancy.

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?

The description is fully self-contained for a read-only lookup tool: it covers input semantics, edge cases (weekends/holidays), failure modes, authorization scope (read:norgesbank), sibling differentiation, and even summarizes return content (rate, date, source). Although an output schema exists, the description adds enough context to use the tool correctly without external references.

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

Parameters5/5

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

The input schema already provides full (100%) coverage with patterns and examples, but the description adds crucial semantic rules: the NOK-anchored requirement (exactly one side must be 'NOK'), the client-side rejection behavior (UNSUPPORTED_CURRENCY_PAIR), and the recommended approach for cross rates (fetch both NOK legs and derive). This depth of guidance goes beyond the schema and is highly actionable.

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 states a specific action ('Fetch the most recent Norges Bank exchange-rate reference') with a clear resource (currency against NOK) and explicitly notes it takes no Norwegian-company input, distinguishing it from sibling tools. It also names an alternative tool for compliance-related needs, further clarifying its unique purpose.

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?

The description clearly states when to use the tool (as the canonical conversion benchmark for tax/accounting obligations) and when not to (for compliance obligations or filing deadlines, directing to get_company_summary). It also provides explicit usage constraints: exactly one side must be 'NOK', and cross rates should be derived manually, which guides correct invocation.

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