One tool connects Pi to Kontra: discover sources and exact rule semantics, validate contracts, profile data, inspect execution plans, compare transformations, measure relationships, and track drift.

No server. No MCP configuration. One short-lived Python process per measurement.

Install

Install Kontra in the Python environment used by your project, then install the Pi package:

pip install "kontra>=0.13.0"
pi install npm:kontra-pi

Or try it for one session:

pi -e git:github.com/Saevarl/kontra-pi

Inside Pi:

> What data sources does Kontra know about?
> Write a contract for warehouse.users. Inspect every rule you use first.
> Explain how contracts/users.yml will execute.
> Validate contracts/users.yml.
> Compare raw.users and warehouse.users on user_id.

Run /kontra doctor if Pi cannot find the intended Python environment. Exact rule lookups require Kontra 0.13.0 or newer.

What it adds

The model receives one kontra tool with a small operation field:

| Need | Operations | |---|---| | Discover | rules, sources, doctor | | Contracts | check, explain, validate | | Profiles | profile, profile_compare, profile_diff | | History | diff | | Probes | compare, relationship |

Collapsed results stay short:

kontra validate contracts/events.yml
✓ 4/4 passed · 100,000 rows

kontra compare raw.users → warehouse.users
Δ 5→5 rows · 0 dropped · 0 added · 3 changed

kontra rules unique
◆ unique · column

Expand a result to see Kontra's semantic summary, the Python executable, and the concrete execution path: metadata, postgres, mssql, clickhouse, duckdb, or polars.

The human-facing slash command stays equally small:

/kontra status
/kontra rules
/kontra sources
/kontra doctor
/kontra gate
/kontra help

Configuration

The extension works without configuration. To select Python explicitly, add .pi/kontra.json:

{
  "python": ".venv/bin/python"
}

The optional completion gate validates selected contracts once after Pi edits a matching file:

{
  "gate": {
    "enabled": true,
    "contracts": ["contracts/users.yml"],
    "include": ["src/**", "models/**", "pipelines/**"]
  }
}

See configuration for every setting, troubleshooting for setup failures, and security for the trust boundary.

Defaults that matter

• Samples default to zero.
• Remote URIs and paths outside the project are rejected by default.
• Named Kontra datasources remain available without placing credentials in the tool request.
• Commands use argument arrays with shell: false.
• Timeout, cancellation, and the 2 MiB output limit are distinct failures.
• Successful and failed results are recursively credential-redacted, with a final context hook as a backstop before model calls.
• The completion gate is off until a project enables it.

Exact counts cost more. Pi asks for tally or bounded samples only when the next decision needs them.

Contract authoring

Kontra owns the rule reference, so Pi reads the catalog from the installed version instead of carrying a stale copy. A compact rules call lists the built-ins; a named lookup returns exact parameters, inclusive boundaries, NULL behavior, counting semantics, tally support, and valid YAML.

Pi can then write a requested contract with its normal file tools and run check, explain, and validate. The extension supplies mechanics, not policy: it does not choose thresholds, allowed values, severity, or freshness windows for you.

Why a native package?

Kontra's official MCP server is the right fit for a shared or remote service. kontra-pi is for local Pi workflows: it uses the project's Python environment, renders directly in the terminal, and requires nothing to keep running.

Development

npm install --ignore-scripts
npm run check
pi -e .

The bridge protocol is deliberately plain JSON over stdin/stdout. Start with DESIGN.md, then read CONTRIBUTING.md.

License

MIT