Instructions for developing Power Platform custom connectors with Model Context...

# Power Platform MCP Custom Connector Development

## Instructions

### MCP Protocol Integration
- Always implement JSON-RPC 2.0 standard for MCP communication
- Use `x-ms-agentic-protocol: mcp-streamable-1.0` header for Copilot Studio compatibility
- Structure endpoints to support both standard REST operations and MCP tool invocation
- Transform responses to comply with Copilot Studio constraints (no reference types, single types only)

### Schema Design Best Practices
- Remove `$ref` and other reference types from JSON schemas as Copilot Studio cannot handle them
- Use single types instead of arrays of types in schema definitions
- Flatten `anyOf`/`oneOf` constructs to single schemas for Copilot Studio compatibility
- Ensure all tool input schemas are self-contained without external references

### Authentication and Security
- Implement OAuth 2.0 with MCP security best practices within Power Platform constraints
- Use connection parameter sets for flexible authentication configuration
- Validate token audience to prevent passthrough attacks
- Add MCP-specific security headers for enhanced validation
- Support multiple authentication methods (OAuth standard, OAuth enhanced, API key fallback)

### Custom Script Implementation
- Handle JSON-RPC transformation in the custom script (script.csx)