Access suppliers and invoices via the Coupa REST API

Steps

1. Obtain API credentials from your Coupa instance administrator; Coupa supports OAuth 2.0 (recommended for integrations) and API key authentication — request an OAuth client ID and secret from Coupa Setup > OAuth2/OpenID Connect Clients.
2. For OAuth, POST to https://{instance}.coupahost.com/oauth2/token with 'grant_type=client_credentials', 'client_id', and 'client_secret'; the base URL uses your Coupa instance subdomain.
3. Include 'Authorization: Bearer {access_token}' and 'Accept: application/json' headers; by default Coupa returns XML — the Accept header is required to receive JSON.
4. List suppliers with GET https://{instance}.coupahost.com/api/suppliers; use query parameters like 'status=active' and standard pagination params 'offset' and 'limit'; filter with 'name[contains]' or other field-specific filter patterns.
5. Access invoices with GET /api/invoices; filter by 'status', 'date-range', or 'supplier[name]' using Coupa's query syntax; include 'invoice_lines' in the response by appending '?fields[invoice_lines]=true' or using the expand parameter.
6. Create or update a supplier by POSTing or PUTting to /api/suppliers with the supplier JSON body; required fields typically include 'name', 'status', and contact information — refer to your Coupa instance's API documentation for required fields as they can vary by configuration.