--- layout: default --- # systemPrompt: Configurando el Comportamiento
**String simple:** ```typescript const agent = createAgent({ model: "mistral:mistral-large-latest", tools: [weatherTool], systemPrompt: "Eres un asistente meteorológico. Sé conciso y preciso.", }); ``` **SystemMessage (para features avanzados como cache de Anthropic):** ```typescript import { SystemMessage } from "langchain"; const agent = createAgent({ model: "anthropic:claude-sonnet-4-6", tools: [weatherTool], systemPrompt: new SystemMessage({ content: [ { type: "text", text: "Eres un experto en clima...", cache_control: { type: "ephemeral" } } ], }), }); ```