USDC has become the primary currency for AI agents in the machine economy, overshadowing AI-themed tokens like FET, TAO, and RENDER. Unlike these speculative tokens, USDC facilitates seamless, sub-second transactions essential for AI operations, which traditional payment systems cannot support due to high fees and slow processing times. The activation of the x402 protocol in 2025, which utilizes the previously unused HTTP 402 status code, has enabled AI agents to make direct payments using USDC without human intervention, revolutionizing machine-to-machine transactions. Circle's 2026 data reveals that over 98% of AI-driven payments are conducted using USDC, with average transactions amounting to $0.31. This shift underscores USDC's role as a fundamental component of the machine internet, akin to TCP/IP and HTTP. The stablecoin's integration into the machine economy highlights its efficiency in handling micropayments, contrasting with the volatility and speculative nature of AI-themed tokens, which remain largely unused by AI agents. The rise of USDC in the AI economy reflects a broader trend where traditional financial systems adapt to technological advancements. As AI agents increasingly drive on-chain trading volumes, projected to reach $5 billion daily by 2027, USDC's role as a stable, fiat-backed currency becomes crucial in facilitating these transactions, positioning it as a cornerstone of the evolving digital economy.