Your team wants Copilot ' s suggestions to reflect knowledge of internal library APIs that...

An MCP server exposing the internal documentation is the appropriate solution because Model Context Protocol extends Copilot with information and capabilities located outside the repository ' s native context. GitHub describes MCP as a mechanism for integrating Copilot with external systems, enabling it to obtain context or invoke functionality that would otherwise be unavailable from the codebase alone.

This architecture is appropriate for proprietary library documentation because the internal API knowledge can remain centrally maintained rather than being duplicated into every repository. The MCP integration can expose a controlled documentation lookup/search capability, allowing Copilot to retrieve relevant definitions, usage patterns, or internal API information when required.

Option A is inferior because copilot-instructions.md is designed for concise repository-specific instructions and conventions, not as a substitute for a potentially large external documentation corpus. GitHub recommends it for persistent guidance such as building, testing, and repository conventions. Option C would remove context rather than add proprietary knowledge. Plan mode affects workflow sequencing and does not provide new external information.

Study Guide Reference Topics: Implement Tool Use and Environment Interaction; MCP-based context augmentation; external knowledge integration; tool-mediated retrieval.

===============