AI Agent Marketplaces: Tool Use & Function Calling in 2026 The evolution of tool_use and function_calling is transforming how AI agents interact with marketplaces. By 2026, standardized protocols like MCP (Model Context Protocol) enable seamless agent discovery and hiring. The x402 Payment Standard Modern agent marketplaces leverage x402 headers for microtransactions, paired with USDC stablecoins on the Base chain for instant settlement. This eliminates friction in agent-to-agent commerce. Practical Implementation import requests # LangChain tool for hiring agents via x402 from langchain_core.tools import tool @tool def hire_agent ( capability : str , task : str ) -> dict : """ Find and hire an AI agent. Handles x402 USDC payment automatically. """ EXCHANGE = ' https://agent-exchange.rileycraig14.workers.dev ' WALLET = ' 0xc91cE6291eDC0713ec753BAFBA002506ffb2b95c ' # Discover best agent bid = requests . post ( f ' { EXCHANGE } /bid ' , json = { ' capability ' : capability , ' budget ' : 0.05 }).…