Mettle

Mettle is a digital-only business bank account brand for UK sole traders, freelancers, and small limited companies, wholly owned by NatWest Group and originally built with Capco. It has no physical branches and is run on separate technology from the core NatWest bank, offering an app-based current account with a UK sort code and account number, invoicing, bookkeeping, tax tools, and a free FreeAgent accounting integration. As a NatWest Group brand, Mettle participates in UK Open Banking through NatWest Group's "Bank of APIs" developer platform, publishing PSD2 / OBIE-conformant APIs - a public, unsecured Open Data (Product) API describing its business current accounts, plus the FAPI-secured Read/Write family (Account & Transaction Information, Payment Initiation, and Confirmation of Funds). Read/Write access runs against a live production gateway (api.openbanking.prd-mettle.co.uk) secured with OAuth2/OIDC, mutual-TLS client authentication, and PSD2 strong customer authentication using OBIE/eIDAS certificates, onboarded via the Bank of APIs portal. Mettle is delivered under NatWest Group's FCA-authorised banking group and is a challenger/digital proposition rather than one of the CMA9 mandated brands.

Mettle publishes 6 APIs on the APIs.io network, including ATM API, BCA API, Branch API, and 3 more. Tagged areas include Financial-Services, Banking, Business Banking, Open Banking, and PSD2.

Mettle’s developer surface includes authentication, sandbox, documentation, engineering blog, support, and 23 more developer resources.

🌐 Visit website 📡 Source on GitHub

39.5/100 developing ▬ flat Agent 39/100 agent native saas Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

AccessSelf serve

1 APIs

Financial-Services Banking Business Banking Open Banking PSD2 OBIE FAPI United Kingdom Payments Account Information Challenger Bank Fintech

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 39.5/100 · developing

Contract Quality 6.9 / 21

Developer Ergonomics 3.5 / 17

Access Clarity 9.7 / 17

Operational Transparency 0.0 / 11

Contract Governance 1.9 / 10

Discoverability 6.5 / 9

Regulatory Posture 10.6 / 15

Agent readiness — 39/100 · agent native

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 6 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 4 / 4

Delegated User Identity 6 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 6 / 6

Agentic Commerce Well-Known Document 0 / 5

Regulatory Posture applies to this provider. Its tags matched the Banking & Open Finance regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics does not apply to this provider. The published contracts declare no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's denominator entirely — not scored zero. A reference or data API is not deficient for being unable to upsert.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/mettle: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 9

Individual APIs this provider publishes, each with its own machine-readable definition.

Mettle Account and Transaction API

OBIE Read/Write Account & Transaction Information (AIS) API for Mettle business current accounts, exposing accounts, balances, transactions, and related resources to FCA-authori...

Mettle Payment Initiation API

OBIE Read/Write Payment Initiation Services (PIS) API for Mettle, allowing FCA-authorised third parties to initiate domestic and other payments from a customer's Mettle account ...

Mettle Confirmation of Funds API

OBIE Read/Write Confirmation of Funds (CBPII) API for Mettle, letting card-based payment instrument issuers confirm whether funds are available on a customer's Mettle account. F...

Mettle ATM API

Endpoint for getting ATM data

Mettle BCA API

Endpoint for getting Business Current Account data

Mettle Branch API

Endpoint for getting Branch data

Mettle CCC API

Endpoint for getting Commercial Credit Card data

Mettle PCA API

Endpoint for getting Personal Current Account data

Mettle SME API

Endpoint for getting Unsecured SME Loan data

Scroll for all 9

Open Collections 1

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Open Data API

OPEN COLLECTION

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Mettle Authentication

oauth2/openIdConnect/mutualTLS · 3 schemes

SECURITY

Mettle Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Scopes 1

OAuth scopes governing access to this provider's APIs.

Mettle Scopes

4 scopes · authorizationCode/clientCredentials

4 scopes

SCOPES

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Mettle Agentic Access

12 operations

12 operations · 0 acting

AGENTIC

Resources

Get Started 2

Portal, sign-up, and the first successful call

Sandbox

Sandbox

DeveloperPortal

DeveloperPortal

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 5

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

WellKnown

WellKnown

X-MCPServerCandidate

X-MCPServerCandidate

LLMsTxt

LLMsTxt

AgentSkill

AgentSkill

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Conformance

Conventions

Idempotency

ErrorCatalog

Lifecycle

DataModel

Access & Security 4

Authentication, authorization, and security posture

DomainSecurity

Authentication

OAuthScopes

Compliance

Operate 3

Status, limits, changes, and where to get help

Deprecation

Deprecation

StatusPage

StatusPage

Support

Support

Commercial 2

Pricing, plans, and the legal terms of use

TermsOfService

TermsOfService

PrivacyPolicy

PrivacyPolicy

Company 3

The organization behind the API

Website

Website

Blog

Blog

LinkedIn

Other 2

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

Overlay

Overlay

Source (apis.yml)

aid: mettle
url: https://raw.githubusercontent.com/api-evangelist/mettle/refs/heads/main/apis.yml
name: Mettle
kind: company
description: Mettle is a digital-only business bank account brand for UK sole traders, freelancers, and small limited companies,
  wholly owned by NatWest Group and originally built with Capco. It has no physical branches and is run on separate technology
  from the core NatWest bank, offering an app-based current account with a UK sort code and account number, invoicing, bookkeeping,
  tax tools, and a free FreeAgent accounting integration. As a NatWest Group brand, Mettle participates in UK Open Banking
  through NatWest Group's "Bank of APIs" developer platform, publishing PSD2 / OBIE-conformant APIs - a public, unsecured
  Open Data (Product) API describing its business current accounts, plus the FAPI-secured Read/Write family (Account & Transaction
  Information, Payment Initiation, and Confirmation of Funds). Read/Write access runs against a live production gateway (api.openbanking.prd-mettle.co.uk)
  secured with OAuth2/OIDC, mutual-TLS client authentication, and PSD2 strong customer authentication using OBIE/eIDAS certificates,
  onboarded via the Bank of APIs portal. Mettle is delivered under NatWest Group's FCA-authorised banking group and is a challenger/digital
  proposition rather than one of the CMA9 mandated brands.
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: false
  label: Hosted service · you call their endpoint
  confidence: medium
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Self-serve signup
  confidence: medium
  source:
  - authentication
  generated: '2026-07-23'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
tags:
- Financial-Services
- Banking
- Business Banking
- Open Banking
- PSD2
- OBIE
- FAPI
- United Kingdom
- Payments
- Account Information
- Challenger Bank
- Fintech
tags_raw:
- Financial Services
- Banking
- Business Banking
- Open Banking
- PSD2
- OBIE
- FAPI
- United Kingdom
- Payments
- Account Information
- Challenger Bank
- Fintech
created: '2026-07-23'
modified: '2026-07-23'
specificationVersion: '0.23'
apis:
- aid: mettle:mettle-account-transaction-api
  name: Mettle Account and Transaction API
  description: OBIE Read/Write Account & Transaction Information (AIS) API for Mettle business current accounts, exposing
    accounts, balances, transactions, and related resources to FCA-authorised third parties. FAPI-secured with OAuth2/OIDC,
    mTLS, and PSD2 strong customer authentication.
  humanURL: https://www.bankofapis.com/products/accounts/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v3.1/aisp
  tags:
  - Account Information
  - Transaction
  - AIS
  tags_raw:
  - Account Information
  - Transactions
  - AIS
  properties:
  - type: Documentation
    url: https://www.bankofapis.com/products/accounts/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/accounts/documentation/mettle
- aid: mettle:mettle-payment-initiation-api
  name: Mettle Payment Initiation API
  description: OBIE Read/Write Payment Initiation Services (PIS) API for Mettle, allowing FCA-authorised third parties to
    initiate domestic and other payments from a customer's Mettle account with their consent. FAPI-secured with OAuth2/OIDC,
    mTLS, and PSD2 strong customer authentication.
  humanURL: https://www.bankofapis.com/products/payments/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v3.1/pisp
  tags:
  - Payment Initiation
  - Payments
  - PIS
  properties:
  - type: Documentation
    url: https://www.bankofapis.com/products/payments/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/payments/documentation/mettle
- aid: mettle:mettle-confirmation-of-funds-api
  name: Mettle Confirmation of Funds API
  description: OBIE Read/Write Confirmation of Funds (CBPII) API for Mettle, letting card-based payment instrument issuers
    confirm whether funds are available on a customer's Mettle account. FAPI-secured with OAuth2/OIDC, mTLS, and PSD2 strong
    customer authentication.
  humanURL: https://www.bankofapis.com/products/card-based-payments/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v3.1/cbpii
  tags:
  - Confirmation of Funds
  - CBPII
  - Funds Check
  properties:
  - type: Documentation
    url: https://www.bankofapis.com/products/card-based-payments/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/card-based-payments/documentation/mettle
- aid: mettle:mettle-atm-api
  name: Mettle ATM API
  description: Endpoint for getting ATM data
  humanURL: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v2.3
  tags:
  - ATM
  properties:
  - type: OpenAPI
    url: openapi/mettle-atm-api-openapi.yml
  - type: Documentation
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
- aid: mettle:mettle-bca-api
  name: Mettle BCA API
  description: Endpoint for getting Business Current Account data
  humanURL: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v2.3
  tags:
  - BCA
  properties:
  - type: OpenAPI
    url: openapi/mettle-bca-api-openapi.yml
  - type: Documentation
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
- aid: mettle:mettle-branch-api
  name: Mettle Branch API
  description: Endpoint for getting Branch data
  humanURL: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v2.3
  tags:
  - Branch
  properties:
  - type: OpenAPI
    url: openapi/mettle-branch-api-openapi.yml
  - type: Documentation
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
- aid: mettle:mettle-ccc-api
  name: Mettle CCC API
  description: Endpoint for getting Commercial Credit Card data
  humanURL: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v2.3
  tags:
  - CCC
  properties:
  - type: OpenAPI
    url: openapi/mettle-ccc-api-openapi.yml
  - type: Documentation
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
- aid: mettle:mettle-pca-api
  name: Mettle PCA API
  description: Endpoint for getting Personal Current Account data
  humanURL: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v2.3
  tags:
  - PCA
  properties:
  - type: OpenAPI
    url: openapi/mettle-pca-api-openapi.yml
  - type: Documentation
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
- aid: mettle:mettle-sme-api
  name: Mettle SME API
  description: Endpoint for getting Unsecured SME Loan data
  humanURL: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  baseURL: https://api.openbanking.prd-mettle.co.uk/open-banking/v2.3
  tags:
  - SME
  properties:
  - type: OpenAPI
    url: openapi/mettle-sme-api-openapi.yml
  - type: Documentation
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
  - type: APIReference
    url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
common:
- type: CapabilityMap
  url: capabilities/mettle-capability-edges.yml
  name: Mettle Business Capability Map
- type: AgenticAccess
  url: agentic-access/mettle-agentic-access.yml
- type: DomainSecurity
  url: security/mettle-domain-security.yml
- type: Authentication
  url: authentication/mettle-authentication.yml
- type: OAuthScopes
  url: scopes/mettle-scopes.yml
- type: Conformance
  url: conformance/mettle-conformance.yml
- type: Compliance
  url: https://www.bankofapis.com/products/natwest-group-open-banking
- type: Conventions
  url: conventions/mettle-conventions.yml
- type: Idempotency
  url: conventions/mettle-conventions.yml
- type: ErrorCatalog
  url: errors/mettle-problem-types.yml
- type: Lifecycle
  url: lifecycle/mettle-lifecycle.yml
- type: Deprecation
  url: https://www.bankofapis.com/products/natwest-group-open-banking
- type: DataModel
  url: data-model/mettle-data-model.yml
- type: WellKnown
  url: well-known/mettle-well-known.yml
- type: X-MCPServerCandidate
  url: mcp/mettle-mcp.yml
  note: 'Renamed from MCPServer 2026-09-03 (roadmap#247): the manifest self-describes as status: candidate — a tool list derived
    from the published API contracts, not an existing server. The scorer already read the manifest and reported mcp_server
    correctly; the MCPServer type was crediting the artifact-type surfaces with a server that does not exist.'
- type: LLMsTxt
  url: llms/mettle-llms.txt
- type: Overlay
  url: overlays/mettle-open-data-api-overlay.yaml
- type: Sandbox
  url: https://developer.sandbox.natwest.com/
- type: AgentSkill
  url: skills/_index.yml
- type: Website
  url: https://www.mettle.co.uk/
- type: DeveloperPortal
  url: https://www.bankofapis.com/
- type: Documentation
  url: https://www.bankofapis.com/products/natwest-group-open-banking/products-and-locations/documentation/mettle
- type: StatusPage
  url: https://www.bankofapis.com/performance/service-interruptions
- type: Blog
  url: https://www.mettle.co.uk/blog/
- type: LinkedIn
  url: https://www.linkedin.com/company/join-mettle
- type: Support
  url: https://www.mettle.co.uk/contact-us/
- type: TermsOfService
  url: https://www.mettle.co.uk/docs/terms-and-conditions/1.5.pdf
- type: PrivacyPolicy
  url: https://www.mettle.co.uk/privacy-notice/
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

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