The original title is: "What Is AI Agent Tool Calling? MCP, Function Calling, and A2A Explained (2026)"

Short summary

A detailed technical explainer of AI agent tool calling protocols in 2026: function calling (LLM emits structured JSON), MCP (standardizes tool discovery and execution via JSON-RPC), and A2A (agent-to-agent delegation). The article argues protocol connectivity is largely solved, with MCP as the de facto standard, and the new bottleneck is tool quality—context efficiency, multi-user authorization, audits, and execution reliability. Practical recommendations include dynamic tool loading and delegated OAuth for production agents.

• •Function calling, MCP, and A2A are complementary protocols for agent-to-system and agent-to-agent communication
• •MCP is the de facto connectivity standard with native support in Claude Code, Cursor, and Windsurf
• •Scaling bottleneck has shifted from protocol connectivity to tool quality: context tax, authorization, audits, and reliability
• •Recommends dynamic tool loading and delegated OAuth with audit logs for production multi-user agents

Generated with AI, which can make mistakes.