# Mettle

**Canonical:** https://apis.io/providers/mettle/  
**Website:** https://www.mettle.co.uk/  
**APIs profiled:** 4

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.

## Kin Score — 45.2 / 100 (developing)

Scored 2026-08-20 under rubric 0.12.0. Trend: flat (+0.0 from 45.2).

| Facet | Score |
|---|---|
| Discoverability | 92.6 |
| Contract Quality | 37.1 |
| Governance | 30.3 |
| Contract Governance | 30.3 |
| Operational Transparency | 0.0 |
| Developer Ergonomics | 20.8 |
| Commercial Clarity | 57.1 |
| Access Clarity | 57.1 |

Regulatory layer — **Banking & Open Finance**: 81.0 (matched via tags).

## Agent readiness — 36.5 (agent-ready)

| Dimension | Value |
|---|---|
| Spec Presence | yes |
| Agentic Access | derived |
| Reversibility Documented | na |
| MCP Server | no |
| Auth Clarity | yes |
| Idempotency | na |
| Error Semantics | documented |
| OpenAPI Examples | no |
| Rate Limit Signal | no |
| Event Surface Described | no |
| Agent Skills | derived |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | na |

## Access

Self-serve signup — onboarding: self-serve, pricing: unknown, trial: no (confidence: medium).

## APIs (4)

- **Mettle Open Data Product API** — Mettle's public, unsecured UK Open Banking Open Data (Product) API, exposing reference information about the business current accounts Mettle offers to sole traders and limited ...
- **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...

## MCP servers (1)

- **Mettle MCP Server**

## Agentic access (1)

- **Mettle Agentic Access** — 12 operations

## Security (2)

- **Mettle Authentication** — oauth2/openIdConnect/mutualTLS · 3 schemes
- **Mettle Domain Security** — TLSv1.3 · HSTS · DMARC

## Tags

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

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/mettle/). Scores are computed from the provider's own public artifacts under a published rubric.