fml

README

FML (Frags Modeling Language)

FML is a compact, human-readable Domain Specific Language designed for defining complex LLM pipelines. It compiles to structured Frags YAML plans, enabling structured outputs, tool integration, and iterative multi-session workflows.

Features

• Concise Syntax: A clean, indentation-sensitive language for LLM pipeline definition.
• Session-Based Pipelines: Organize your LLM tasks into logical, dependent sessions.
• Automatic Schema Assembly: Generates JSON Schema automatically from session definitions.
• Tool & MCP Support: Easily declare tool requirements (MCP, API CP, functions) with optional method allowlisting.
• Metadata Preservation: Comments are preserved and mapped to JSON Schema descriptions.
• Bi-directional: Includes a compiler (FML -> YAML) and a decompiler (YAML -> FML).
• IDE Support: Language Server Protocol (LSP) implementation for real-time diagnostics and highlighting.

Installation

# Clone the repository
git clone https://github.com/theirish81/fml.git
cd fml

# Build the CLI
go build -o fml main.go

Usage

The FML CLI is powered by Cobra, providing a robust interface with built-in help.

Compiling FML to YAML

./fml compile test.fml -o plan.yaml

Decompiling YAML to FML

./fml decompile plan.yaml -o restored.fml

Help

You can always use the --help flag to see available commands and options:

./fml --help
./fml compile --help

Language Overview

system("You are a research assistant.")

parameter("topic", type=string)
parameter("limit", type=int, default=5)

session("research") {
    use search
    
    + Search for the latest trends in {{ .params.topic }}.
    - Summarize the top {{ .params.limit }} results.

    schema {
        trends: string[]
        summary: string
    }
}

For more details on the language, see frags-dsl-spec.md.

LSP Library

The FML LSP is provided as a library in the ./lsp directory. It can be integrated into Go applications to provide Language Server Protocol capabilities via Stdio, TCP, or WebSocket.

Features supported:

• Syntax Diagnostics (including multi-line system prompts)
• Semantic Tokens (Highlighting including backtick raw strings)
• Autocompletion (Keywords, Types, Attributes)
• Basic Hover

For integration details, see lsp/README.md.

Project Structure

• parser/: Lexer and AST definition.
• compiler/: Logic for DSL to YAML transformation.
• decompiler/: Logic for YAML to DSL transformation.
• lsp/: Language Server Protocol library.
• main.go: CLI entry point.

License

MIT