Frankfurter
Frankfurter is an open-source (MIT) currency exchange rates API that blends foreign-exchange reference rates published by 50+ central banks and monetary authorities. It hosts a free, no-key public endpoint at api.frankfurter.dev (current v2 and frozen v1) and ships as a Docker image for unlimited self-hosting. Historical data extends back to 1948 and covers 201 currencies; the API serves JSON, NDJSON, and CSV.
Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.
API Evangelist profiles Frankfurter the way a machine reads it — 80 machine-readable artifacts across 6 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Frankfurter scores 47.4/100 (developing), with a separate agent-readiness read of 39/100 (agent aware). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.
Kin Score
How this is scored →scored 2026-07-27 · rubric v0.5
How we profile Frankfurter
Each block below is one kind of artifact we hold for Frankfurter. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 6
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Frankfurter Currencies API
Supported currency reference data
Frankfurter current-rates API
Latest foreign exchange rates
Frankfurter historical-rates API
Historical exchange rates for specific dates and periods
Frankfurter metadata API
API reference data like available currencies
Frankfurter Providers API
Central-bank and institutional data providers
Frankfurter Rates API
Blended currency exchange rates
Open Collections 2
Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
Frankfurter API
OPEN COLLECTIONFrankfurter API
OPEN COLLECTIONPricing Plans 1
Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the six things the Kin Score reads for commercial clarity.
Published pricing tiers and plan structures.
Rate Limits 1
Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.
Documented rate limits and quota policies.
Frankfurter Rate Limits
RATE LIMITSFeatures 10
The notable capabilities this provider advertises, captured as structured features so they can be searched and compared instead of read one landing page at a time.
Notable capabilities this provider offers.
Blended Reference Rates
Combines daily FX rates from 50+ central banks and monetary authorities into a consensus-filtered, outlier-rejecting blend.
Multi-Format Output
JSON, NDJSON (streamed), and CSV from the same endpoint.
Historical Time Series
Daily rates back to 1948 with optional week/month downsampling.
201 Currencies
Active and legacy currency coverage with ISO 4217 metadata.
Per-Provider Expansion
`expand=providers` exposes each provider's individual quote so callers can audit the blend, with `excluded: true` flags on outliers and peg overrides.
No Authentication
No keys, no accounts, no monthly or daily caps.
Self-Hostable
Single Docker image with optional SQLite volume mount.
Free Upstream Provider Keys
Optional, no-cost provider keys for Bank Al-Maghrib, Banco de México, Banco Central de Chile, Bank of Thailand, US Federal Reserve, and the Turkish Central Bank widen self-hoste...
Open CORS
GET and OPTIONS allowed from any origin — direct browser use.
Open Source (MIT)
Full source on GitHub; community contributions and fork-friendly.
Scroll within the panel for all 10 ·
Semantic Vocabularies 2
JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.
JSON-LD contexts and semantic vocabularies used across these APIs.
Frankfurter V1 Context
JSON-LDFrankfurter V2 Context
JSON-LDSpectral Rules 2
Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.
Frankfurter API Rules
SPECTRALFrankfurter API Rules
SPECTRALJSON Schema 12
Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.
Standalone JSON Schema definitions for this provider's data models.
amount
JSON SCHEMAbaseIn
JSON SCHEMAbase
JSON SCHEMAcurrencies
JSON SCHEMAdate
JSON SCHEMAratesByDate
JSON SCHEMAratesOnDate
JSON SCHEMArates
JSON SCHEMACurrencyDetail
JSON SCHEMACurrency
JSON SCHEMAProvider
JSON SCHEMARate
JSON SCHEMAScroll within the panel for all 12 ·
JSON Structure 12
JSON Structure captures the data shapes in a form built for tooling — a complement to JSON Schema that keeps the model machine-legible.
JSON Structure definitions describing this provider's data shapes.
V1 Amount Structure
JSON STRUCTUREV1 Base In Structure
JSON STRUCTUREV1 Base Structure
JSON STRUCTUREV1 Currencies Structure
JSON STRUCTUREV1 Date Structure
JSON STRUCTUREV1 Rates By Date Structure
JSON STRUCTUREV1 Rates On Date Structure
JSON STRUCTUREV1 Rates Structure
JSON STRUCTUREV2 Currency Detail Structure
JSON STRUCTUREV2 Currency Structure
JSON STRUCTUREV2 Provider Structure
JSON STRUCTUREV2 Rate Structure
JSON STRUCTUREScroll within the panel for all 12 ·
Examples 8
Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.
Example request and response payloads for these APIs.
V1 Currencies Example
EXAMPLEV1 Rates By Date Example
EXAMPLEV1 Rates Example
EXAMPLEV1 Rates On Date Example
EXAMPLEV2 Currency Detail Example
EXAMPLEV2 Currency Example
EXAMPLEV2 Provider Example
EXAMPLEV2 Rate Example
EXAMPLEScroll within the panel for all 8 ·
Security Posture 1
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Use Cases 7
What developers actually build with this provider — captured so the catalogue answers 'what is this for', not just 'what does this expose'.
What developers build with this provider.
Treasury and Payments Pricing
Embed blended FX rates into invoicing, payouts, and conversion.
E-commerce Storefront Localization
Convert displayed prices into the visitor's currency on page load.
Reporting and Analytics
Backfill historical FX into BI dashboards and finance reports.
Reference Data Maintenance
Sync ISO 4217 currency tables and provider metadata into ERPs.
AI Assistant Tooling
Equip Claude and other MCP-capable agents with the official Frankfurter MCP server (get_rates, convert, list_currencies, list_providers).
Private FX Service
Self-host inside a VPC for compliance-sensitive workloads.
Academic and Research
Long historical series for FX econometric studies.
Scroll within the panel for all 7 ·
Integrations 12
Pre-built integrations with other platforms tell you where this provider already fits in a stack.
Pre-built integrations with other platforms and tools.
European Central Bank
Primary upstream provider (ECB reference rates).
US Federal Reserve
Optional upstream provider via free FED API key.
Bank of Canada
Upstream provider (BOC) included in the blend.
Banco Central do Brasil
Upstream provider (BCB).
Turkish Central Bank
Optional upstream provider via free TCMB key.
Bank of Thailand
Optional upstream provider via free BOT key.
Banco Central de Chile
Optional upstream provider via free BCCh key.
Banco de México
Optional upstream provider via free Banxico key.
Bank Al-Maghrib (Morocco)
Optional upstream provider via free BAM key.
Model Context Protocol
Official MCP server (lineofflight/frankfurter-mcp) registered at the MCP registry.
Docker Hub / GHCR
Container distribution for self-hosting.
GitHub Discussions
Community 'Show and Tell' for libraries and tools built on Frankfurter.
Scroll within the panel for all 12 ·
Solutions 3
Packaged solutions the provider offers on top of the raw API surface.
Packaged solutions this provider offers.
Public Hosted (Free)
api.frankfurter.dev — no key, soft fair-use limits, ideal for prototypes and low-volume production.
Self-Hosted FOSS
Run lineofflight/frankfurter via Docker; no application-level rate limit.
MCP Tooling
Drop the Frankfurter MCP server into any Claude / agent stack for natural-language FX access.
Resources
Every other property we hold for Frankfurter — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Documentation 1
Reference material describing how the API behaves
Agent Surfaces 1
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 2
Pagination, idempotency, versioning, errors, and events
Build 6
SDKs, sample code, and the tooling you integrate with
Access & Security 1
Authentication, authorization, and security posture
Operate 3
Status, limits, changes, and where to get help
Commercial 2
Pricing, plans, and the legal terms of use
Company 1
The organization behind the API
Other 3
Properties that don't map to a standard resource type
← All providers · Data indexed from github.com/api-evangelist/frankfurter · machine-readable index on apis.io