What problem does it solve? Developers integrating an APIMatic-generated .NET SDK often guess operation names, parameter order, and return types, producing calls that fail to compile or send wrong requests. This Skill grounds every call in the SDK's contract sheet so the first call to any endpoint is written correctly. ## Core Features & Use Cases - Method Signature Conventions: Explains the fixed parameter order (non-defaulted params, defaulted params, CancellationToken last) and why named arguments are required for list/search endpoints with many optional parameters. - Request and Response Shapes: Covers building immutable record request bodies with object-initializer syntax and reading the five response envelope variants (nested resource, direct resource, array, nested array, empty). - Use Case: When writing a C# call to a payments list endpoint, load this Skill to copy the exact parameter names from the signature, pass them as named arguments, and correctly iterate the returned IReadOnlyList of items. ## Quick Start Load this skill before writing the first call to an SDK operation so the agent reads the operation's real signature and return type from the contract sheet.