FCP

FCP, or Free Communication Protocol, is a minimal, text-first protocol designed to facilitate communication between two parties over HTTP. It is structured around the concept of "actors," allowing any participant—whether human, AI, or script—to initiate or receive messages by sending and reading text. The protocol addresses the need for straightforward, schema-free interaction, where both parties rely on natural language to negotiate capabilities, exchange information, and handle tasks without requiring specialized SDKs, schemas, or code generation tools.

The core operation of FCP involves client and target actors communicating via HTTP(S) endpoints. The protocol mandates that a conformant target actor must expose such an endpoint, accept POST requests with textual bodies (including plain text, Markdown, or JSON), and respond with a textual body. If a request body parses as JSON, it may be interpreted as such, but otherwise it is treated as plain text. FCP also supports an optional handshake mechanism, where a client actor can query a target actor's capabilities through a GET request to the endpoint, receiving a self-description and details about any optional features.

Negotiation of features such as authentication, streaming, sessions, and other advanced behaviors occurs through natural language during the handshake. For example, if authentication is required, the handshake response describes how to obtain and use credentials. Similarly, if session state is maintained, the protocol specifies how the session identifier is communicated and reused. The protocol does not prescribe any envelope structure, task lifecycle, or capability manifest, deliberately rejecting the complexity found in other agent-to-agent protocols. Instead, it relies on the actors' ability to understand and negotiate requirements in natural language at runtime.

FCP is suitable for developers, system integrators, or anyone seeking to build interoperable systems where communication between actors—human or machine—can be achieved with minimal overhead and maximum flexibility. The protocol is intentionally concise and extensible, with provisions for future support of non-textual or multimodal payloads negotiated via the same text-based handshake.