What is the primary role of API contracts in library usage?

• A. Document internal helper functions only.
• B. Describe the project's build steps.
• C. Define intent and usage; including parameters, return values, side effects, exceptions, and examples.
• D. List team responsibilities.

Answer: (C)

API contracts define how to interact with a library’s public surface. They spell out the intent and usage of each API, including what parameters to pass, what return values to expect, any side effects, the exceptions or error conditions that may be raised, and concrete examples. This clarity gives developers a reliable guide for correct usage, helps ensure consistent behavior across versions, and supports testing and documentation. Internal helper functions, build steps, and team responsibilities describe unrelated aspects and aren’t part of the public contract, since they pertain to implementation details, build processes, or project organization rather than how the library should be consumed.