# Infor LN REST API: documentation, administration and a first call > Source: https://netray.co/erp-help/infor-ln-rest-api-documentation-and-first-call > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: ERP Help ## Short answer LN REST access goes through the Infor ION API gateway. You register an authorized app in ION API, download its .ionapi credentials file, obtain an OAuth 2.0 token and call the LN API endpoints with the bearer token. Official reference material is on the Infor documentation site and the ION API documentation inside your Infor OS portal. ## Kind how-to ## System infor-ln ## Erp Infor LN ## Module ION API / REST ## Query infor ln rest api documentation ## Alternate Queries - infor ln rest api administration guide - infor ion api gateway ln - infor ln rest api token ionapi ## Applies To Infor LN 10.x with Infor OS ION API, on-prem or cloud. Endpoint paths depend on the API and version. ## Steps ### Make a first call **Items:** - In Infor OS, open ION API and confirm the LN API suite is available for your tenant. - Create an Authorized App of type Backend Service, with a service account, and download the .ionapi file. - Read the file: it contains client id (ci), client secret (cs), the token URL parts (pu and ot), the service account keys (saak and sask) and the tenant (ti). - Request a token with the password grant, using saak and sask as username and password and ci and cs as client credentials. - Call the LN API endpoint shown in the ION API documentation for your service, with the header Authorization: Bearer . - Start with a read (GET) of a small entity and check the response before attempting any write. ## Sections ### Where the documentation is **Body:** Three sources matter. The Infor documentation site has the ION API guide and the LN-specific API guides for your release. The ION API application inside Infor OS lists the APIs available to your tenant, with a try-it-out view. The Infor support portal holds version-specific notes and known issues. Because paths and versions differ between releases, always take the endpoint from your own ION API listing, not from a blog post. ### Administration **Body:** Administer access in ION API: authorized apps, service accounts, scopes and which security roles the service account maps to in LN. The service account needs an LN user with the right authorizations, otherwise calls authenticate but fail with authorization errors from LN. Rotate secrets as you would any credential, and keep the .ionapi file out of source control. **Code:** - POST - Content-Type: application/x-www-form-urlencoded - grant_type=password&username=&password=&client_id=&client_secret= ### Choosing REST, BODs or direct database reads **Body:** REST suits request-response integrations and AI tools. BODs suit event-driven exchange. Direct database reads are fastest for analytics but bypass LN business logic and are not appropriate for writes. For AI assistants, a common pattern is read-only SQL or API access for retrieval, and a REST call behind human approval for any write. ## Pitfalls - Using endpoints copied from an old tutorial. - Service account with no LN authorizations. - Committing the .ionapi file to a repository. - Testing writes in production first. - Ignoring token expiry in long-running jobs. ## Ai Angle Netray builds agents that call ION API with a least-privilege service account, show the request before it runs, and hold writes for approval. The model runs on your own GPUs, so credentials and payloads never reach a public AI service. ## Faq ### Where is the Infor LN REST API documentation? **Answer:** Use the Infor documentation site for your LN release and the ION API listing in your Infor OS portal. The latter shows the exact endpoints enabled for your tenant. ### What is an .ionapi file? **Answer:** A JSON credentials file generated for an authorized app. It holds client and service account details needed to request OAuth tokens. ### Can I call LN REST without ION API? **Answer:** In standard deployments the supported route is through ION API. Confirm with Infor for your version if you need another route. ### Why do I get a 401 or 403? **Answer:** 401 usually means a bad or expired token. 403 often means the service account lacks LN authorization for that entity. ## Search terms infor ln rest api, infor ln rest api documentation, infor ln rest api administration guide, infor ion api, ionapi file, infor ln oauth token, infor os ion api gateway, infor ln api first call --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json