Implement MCP Tool Integrations

Implement MCP-enabled tools that the LangGraph agents can use. These tools should simulate access to external data sources such as a 'MarketDataFetcher' (returns mock market trends for a given query), a 'FinancialCalculator' (performs mock ROI, burn rate calculations), and a 'TechValidator' (returns mock expert opinions on technology novelty). Demonstrate how agents within your LangGraph workflow invoke these tools.