Lemma CLI

A command-line interface for the Lemma language.

This package provides the lemma CLI for evaluating, inspecting and serving Lemma specs.

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 evaluate shipping

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

# Provide data values
lemma evaluate tax_calculation income=75000 filing_status="married"

# Provide data as JSON from stdin (lists are passed this way)
cat order.json | lemma evaluate order -

# Explore specs interactively
lemma evaluate --interactive

# Show the inputs, types and rules of a spec
lemma show pricing

# The same as a JSON Schema for the evaluation data
lemma show pricing --json

# Loaded specs grouped by repository
lemma specs
lemma specs --path ./my_project
lemma specs --json
lemma specs --all

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

# Start the MCP server (AI assistant integration)
lemma mcp --path ./engine/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 evaluate shipping
┌───────────────┬───────────┐
│ base_shipping ┆ 8.99 eur  │
├───────────────┼───────────┤
│ express_fee   ┆ 4.99 eur  │
├───────────────┼───────────┤
│ total_cost    ┆ 13.98 eur │
└───────────────┴───────────┘

JSON for tooling:

lemma evaluate shipping --json > output.json

Documentation

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

Contributing

Contributions are very welcome!

License

Apache 2.0