Function Calling / MRKL / Model Context Protocol

Editorial record

Plain-language summary

MRKL proposed a neuro-symbolic architecture in which a router directs a query to discrete expert modules, such as a calculator, database, or API, and merges their outputs. Later function-calling formats let a model emit a structured call that host code executes and feeds back, and the Model Context Protocol standardizes how tools, data sources, and context are exposed to models across applications. The common contribution is a defined boundary and calling convention between the model and outside systems, which enabled reliable access to current data, exact computation, and actions the model cannot perform internally.