Why Byte-Faithful Pass-Through Beats Protocol Translation for Tool-Calling Agents

1. The Siren Song of Universal Protocol Normalization Every backend engineer who builds an LLM proxy experiences the same architectural epiphany: "Why maintain three separate routing engines when I can parse incoming payloads into a single universal struct, mutate the model name, and serialize them into whatever vendor schema the target API expects?" [Claude Code] ───(Anthropic JSON)───> [Unified IR] ───(OpenAI JSON)───> [DeepSeek/OpenAI] This pattern—formalized in popular libraries like LiteLLM and adopted by countless multi-agent proxies—looks elegant on paper. It promises an $O(N+M)$ adapte