> For the complete documentation index, see [llms.txt](https://doc.api.tieto.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.api.tieto.com/portals-and-interfaces/api-gateway.md). # API Gateway The API Gateway is the platform's front door. Every call from a third-party provider passes through it, and it is where identity is established, policy is enforced and traffic is routed to the right bank. ## REST architecture All services exposed through the API Gateway follow REST architecture over HTTPS. This provides a familiar, standardized interface that clients can integrate with quickly and consistently. Payloads use JSON, element names follow ISO 20022, and responses include hypermedia links. ## Security All connections use TLS 1.2 or higher. Clients authenticate using access tokens or API keys, based on your integration requirements. The platform validates client certificates for trust, ownership, expiry and revocation. For PSD2 APIs, the gateway verifies each TPP's current authorization and regulatory roles against the relevant national register on every call. ## Configurability Certificate and schema validation, rate limiting, caching, signature handling, header manipulation and audit logging are all applied here, configurable per operation. See [API Policies](/features/api-policies.md) for the full set. ## Compliance Conditions the gateway can resolve itself are answered directly, without troubling the connected bank — unknown resources, unsupported methods and content types, malformed or inconsistent parameters, certificate and signature failures, token problems, out-of-scope operations, exceeded limits, and upstream connection and timeout failures. Each response is formatted according to Berlin Group standard — it carries a category, a machine-readable code and human-readable text. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://doc.api.tieto.com/portals-and-interfaces/api-gateway.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.