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 pre-1.0. The CLI is stable for most use cases, but breaking changes may occur between minor versions. Pin your dependency version and review the changelog before upgrading.

Installation

cargo install lemma

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 data values
lemma run tax_calculation income=75000 filing_status="married"

# Explore specs interactively
lemma run --interactive

# Show spec structure
lemma schema pricing

# List loaded specs grouped by repository
lemma list
lemma list --prefix ./my_project
lemma list --json

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

# Start the MCP server (AI assistant integration)
lemma mcp --prefix ./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 data 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 – --json 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 --json > output.json

Documentation

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

Contributing

Contributions are very welcome!

License

Apache 2.0