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.
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 Mettle the way a machine reads it — 14 machine-readable artifacts across 1 API, 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 — Mettle scores 39.5/100 (developing), with a separate agent-readiness read of 39/100 (agent native). 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. Every facet and dimension name is a link: it opens that measurement's page on APIs.io, where the rating runs across the whole catalog — the exact checks that feed it, how every profiled provider distributes on it, and who is at the top of it.
Kin Score
How this is scored →scored 2026-09-08 · rubric v0.20.0
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<!-- Kin Score · API Evangelist -->
<a href="https://providers.apievangelist.com/providers/mettle/"
title="Mettle on API Evangelist — API profile and Kin Score">
<img src="https://apis.io/badge/mettle.svg"
alt="Mettle Kin Score — API readiness rating by API Evangelist" width="150" height="150" loading="lazy">
</a>[](https://providers.apievangelist.com/providers/mettle/)<!-- Kin Score · API Evangelist -->
<a href="https://providers.apievangelist.com/providers/mettle/"
title="Mettle on API Evangelist — API profile and Kin Score">
<img src="https://apis.io/badge/mettle/card.svg"
alt="Mettle Kin Score — API readiness rating by API Evangelist" width="340" height="120" loading="lazy">
</a>More shapes, themes and sizes → · Score as JSON · How badges work
How we profile Mettle
Each block below is one kind of artifact we hold for Mettle. 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 9
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.
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 within the panel for all 9 ·
Open Collections 1
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).
Open Data API
OPEN COLLECTIONSecurity Posture 2
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.
Scopes 1
OAuth scopes are the vocabulary of least-privilege access. Profiling them shows exactly what an integration — or an agent acting on a user's behalf — is allowed to do.
OAuth scopes governing access to this provider's APIs.
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.
Resources
Every other property we hold for Mettle — 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.
Get Started 2
Portal, sign-up, and the first successful call
Documentation 1
Reference material describing how the API behaves
Agent Surfaces 5
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 6
Pagination, idempotency, versioning, errors, and events
Access & Security 4
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 3
The organization behind the API
Other 2
Properties that don't map to a standard resource type
← All providers · Data indexed from github.com/api-evangelist/mettle · machine-readable index on apis.io
This is an independent, third-party profile of Mettle, published by API Evangelist. We do not operate, host, resell, or support these APIs, and we are not affiliated with or endorsed by the company unless stated above. Everything here is built from publicly available information — the company's own site, developer portal, documentation, public repositories, and the specifications it publishes for public use. Nothing is obtained by breaching a system, defeating an access control, or using credentials.
The Kin Score and Agent Readiness rating are independently calculated assessments of a company's public API artifacts, scored against a published rubric. They are not certifications, endorsements, security assessments, or audits.
Corrections, re-scores, and removal are free — no partnership or purchase required, and you do not need to justify the request. A removed company is recorded as unrated, never scored zero for having asked. Acknowledgement within one business day; removal within two.
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