# Engg Skills Common

> >-

- **Type:** Skill
- **Install:** `agentstack add skill-jskherman-engg-skills-engg-skills-common`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [jskherman](https://agentstack.voostack.com/s/jskherman)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** Apache-2.0
- **Upstream author:** [jskherman](https://github.com/jskherman)
- **Source:** https://github.com/jskherman/engg-skills/tree/main/skills/engg-skills-common

## Install

```sh
agentstack add skill-jskherman-engg-skills-engg-skills-common
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# engg-skills-common (Shared Library)

## Overview

This is a developer-facing skill describing the shared Python package
`engg_skills_common`. All engineering-skill scripts import from it. It
contains:

- `io.py` — JSON envelope, `write_json`, number parsing helpers.
- `notices.py` — warning strings, source notices, and the
  `write_license_notification` helper for the first-use
  `LICENSE_NOTIFICATION.txt` artifact.
- `dimensionless.py`, `units.py`, `stats.py`, `doe.py`, `spc.py`,
  `balances.py`, `fluids.py`, `heat_transfer.py` — original pure-Python
  helpers.
- `property_backends.py` — thin wrappers around `thermo`, `chemicals`,
  `fluids`, `ht` with soft imports and engineering defaults for LPG.
- `vle.py`, `separations.py`, `reactor.py`, `separator.py`, `valves.py`,
  `two_phase.py`, `convection.py`, `coda.py`, `causal.py`,
  `timeseries.py`, `amine.py`, `merox.py` — newer domain modules.

The package is intentionally light: heavy dependencies (`pymc`, `arviz`,
`statsmodels`) are NEVER imported at module load time. They are loaded
lazily inside the scripts that need them.

## When to Use

- Authoring a new skill that needs a shared helper.
- Adding a new shared module for a class of calculations.
- Reviewing the standard JSON envelope or notification pattern.

## Don't use for

- Running engineering calculations directly — go through a skill script.
- Adding a heavy ML dependency at module load; use the script PEP-723
  header instead.

## Conventions

- All functions take keyword arguments for clarity in scripts.
- All functions return plain dicts so `json.dumps` works.
- Validation errors raise `ValueError`; missing optional libraries raise
  a clear `RuntimeError` via `_require_library`.
- Names are descriptive with unit suffixes (e.g. `rho_kg_m3` not `rho`).

## Procedure

1. Read this SKILL.md and any referenced files needed for the task.
2. Use scripts from `scripts/` when a deterministic calculation or check is available.
3. Preserve stated assumptions, warnings, and scope limits in the final answer.

## Pitfalls

- Adding a heavy dependency import at the top of a module instead of
  using `_require_library` inside the function.
- Returning numpy arrays or pandas Index objects in a result dict — they
  do not JSON-serialise. Convert to lists / floats first.
- Mutating a caller's input list/dict in place.
- Writing a function that does I/O. The shared library does math and
  light orchestration; I/O belongs in the script.

## Tests

Tests live in `tests/`. Each module should have a dedicated
`test_.py` with at least three tests covering: a typical case,
an edge case (zero / empty), and an error case.

## Verification

- Run `.venv/bin/python -m pytest -q` or `pytest -q` from the repository root after changing shared modules.
- Confirm scripts that import `engg_skills_common` resolve it from `skills/engg-skills-common`.

## References

- See each skill's SKILL.md for the user-facing usage.
- `skills/engineering-skill-creator/references/script_template.md` for
  the canonical CLI shape that consumes this library.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [jskherman](https://github.com/jskherman)
- **Source:** [jskherman/engg-skills](https://github.com/jskherman/engg-skills)
- **License:** Apache-2.0

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-jskherman-engg-skills-engg-skills-common
- Seller: https://agentstack.voostack.com/s/jskherman
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.