# 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](https://github.com/lemma/lemma/blob/main/CHANGELOG.md) before upgrading.
## Installation
```bash
cargo install lemma
```
After installation the `lemma` binary is available on your PATH.
## Common commands
```bash
# 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
```bash
lemma run shipping
# Output:
# ┌───────────────┬──────────────────────────────────────────────────────┐
# │ Rule ┆ Evaluation │
# ╞═══════════════╪══════════════════════════════════════════════════════╡
# │ express_fee ┆ 4.99 │
# │ ┆ ... │
# └───────────────┴──────────────────────────────────────────────────────┘
```
Enable raw mode to pipe results:
```bash
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