Lemma CLI

A command-line interface for the Lemma language.

This package provides the lemma CLI for running, inspecting, and serving Lemma specs. It ships alongside the lemma-engine crate and exposes the same deterministic, auditable evaluation pipeline from the terminal.

Status

Lemma is still early-stage and not yet recommended for production use. Expect breaking changes and evolving commands while the toolchain stabilizes.

Installation

cargo install lemma-cli

After installation the lemma binary is available on your PATH.

Common commands

# Evaluate a spec (all rules)
lemma run shipping

# Evaluate specific rules
lemma run tax_calculation --rules=tax_owed

# Provide fact values
lemma run tax_calculation income=75000 filing_status="married"

# Explore specs interactively
lemma run --interactive

# Show spec structure
lemma show pricing

# List available specs
lemma list ./documentation/examples

# Start the HTTP server
lemma server --port 8012 --dir ./documentation/examples

# Start the MCP server (AI assistant integration)
lemma mcp --dir ./documentation/examples

Each command supports --help for full usage details.

Features

• Deterministic evaluations – same audit trail as the engine library
• Interactive mode – select specs, rules, and facts without typing full paths
• HTTP server – evaluate specs over REST, perfect for integration tests and dashboards
• MCP server – expose Lemma to AI assistants via the Model Context Protocol
• Machine-readable output – --raw flag for tooling and pipelines

Example session

lemma run shipping

# Output:
# ┌───────────────┬──────────────────────────────────────────────────────┐
# │ Rule          ┆ Evaluation                                           │
# ╞═══════════════╪══════════════════════════════════════════════════════╡
# │ express_fee   ┆ 4.99                                                 │
# │               ┆    ...                                               │
# └───────────────┴──────────────────────────────────────────────────────┘

Enable raw mode to pipe results:

lemma run shipping --raw > output.json

Documentation

• CLI reference: https://github.com/benrogmans/lemma/blob/main/documentation/CLI.md
• Language guide: https://benrogmans.github.io/lemma/
• API docs (engine): https://docs.rs/lemma-engine
• Examples: https://github.com/benrogmans/lemma/tree/main/documentation/examples
• Roadmap: https://github.com/benrogmans/lemma/blob/main/documentation/roadmap.md

Contributing

Contributions are very welcome! See documentation/contributing.md and the project roadmap for ideas.

License

Apache 2.0