> ## Documentation Index > Fetch the complete documentation index at: https://openrouter.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # System ## Supported Types ### ```go theme={null} system := components.CreateSystemStr(string{/* values here */}) ``` ### ```go theme={null} system := components.CreateSystemArrayOfAnthropicTextBlockParam([]components.AnthropicTextBlockParam{/* values here */}) ``` ## Union Discrimination Use the `Type` field to determine which variant is active, then access the corresponding field: ```go theme={null} switch system.Type { case components.SystemTypeStr: // system.Str is populated case components.SystemTypeArrayOfAnthropicTextBlockParam: // system.ArrayOfAnthropicTextBlockParam is populated } ```