Web Services Description Language — the contract definition for SOAP services.
WSDL defines the complete SOAP service contract:
- types: XSD schemas for request/response data
- message: named input/output message shapes
- portType: grouped operations (like an interface)
- binding: maps operations to SOAP protocol details
- service: the actual endpoint URL
Always generate client code from the WSDL rather than hand-coding SOAP. When the carrier updates their WSDL, regenerate and diff to catch breaking changes.