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Run npx skillmds@latest add ashfordeou/engineering-margins in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Is Engineering Margins free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under Apache-2.

Who published Engineering Margins?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Engineering Margins by ashfordeou — Agent Skill

Name: Engineering Margins
Author: ashfordeOU

Engineering Margins

Use when you must compute the margin of safety for a structural element and state it in an engineering report: compare the allowable load against the applied load, express the stress margin as a unitless decimal or a percent, and produce the pass/fail verdict on the limit basis or ultimate basis. Produces the margin of safety, the margin percent, the limit margin, and the one-line report sentence with consistent units in newtons. Trigger: margin of safety, engineering report, allowable load, limit load, ultimate load, stress margin.

ashfordeOU Updated Sep 17, 2026

File contents

Engineering Margins (cross-cutting/documentation/engineering-margins)

Use when the task is the margin of safety for a structural element and the report sentence that carries it: allowable versus applied load, the limit basis and the ultimate basis, and the pass/fail verdict. This is the cross-cutting documentation-pack discipline for reporting margins; strength and allowable computation leaves live in the structures pack.

Domain quick reference

Quantity convention: allowable and applied values are loads in newtons (N). Stresses in pascals (Pa) work identically because the margin is unitless, but a single call must never mix units: pick one unit (all N, or all Pa) and state it in the report. The Pa/MPa mix is the known bug class.
Margin of safety MS = (allowable / applied) - 1, unitless decimal.
MS >= 0 passes (allowable at least equals applied); MS < 0 fails.
Margin percent = MS * 100, in percent.
Limit margin ML = (limit_allowable / limit_applied) - 1, the limit basis check.
Example: allowable 125000 N, applied 100000 N: MS = 0.25, pass.
Example: allowable 90000 N, applied 100000 N: MS = -0.10, fail.

Workflow

Pick the quantity and unit convention (loads in newtons), the same unit for both inputs.
Compute the margin with margin_of_safety.
Express it as a percent with margin_percent.
Check the limit basis with limit_margin.
Get the verdict with margin_verdict.
Write the report sentence with report_margin, naming the basis (limit or ultimate).

Pitfalls

Mixing units: Pa for one input and MPa for the other. The margin formula divides one value by the other, so mixed units silently corrupt the result. Pick one unit for both inputs.
Reading a negative margin as an error: MS < 0 is a real fail verdict to report, not an exception.
Forgetting the basis: the report sentence must state limit or ultimate.
Reporting the percent margin as the decimal margin: margin_percent returns MS * 100, not MS.
Writing the margin without the verdict: the report sentence carries the margin, the basis, and the pass/fail verdict.

Behavior contract (gate 3)

The margin logic is exercised by the gate 3 contract test: scripts/test_engineering_margins.py against scripts/engineering_margins_logic.py (stdlib unittest, offline). Run: python3 scripts/test_engineering_margins.py

Compliance

Standards referenced, not reproduced: FAR-25 and CS-25 are referenced for the margin-of-safety practice; the margin formula is common structural-analysis methodology, summary-only per standards-map.yaml.
compliance: STANDARDS-REF, gated: false.

---name: engineering-marginsdescription: Use when you must compute the margin of safety for a structural element and state it in an engineering report: compare the allowable load against the applied load, express the stress margin as a unitless decimal or a percent, and produce the pass/fail verdict on the limit basis or ultimate basis. Produces the margin of safety, the margin percent, the limit margin, and the one-line report sentence with consistent units in newtons. Trigger: margin of safety, engineering report, allowable load, limit load, ultimate load, stress margin.license: Apache-2.0---# Engineering Margins (cross-cutting/documentation/engineering-margins)Use when the task is the margin of safety for a structural elementand the report sentence that carries it: allowable versus appliedload, the limit basis and the ultimate basis, and the pass/failverdict. This is the cross-cutting documentation-pack discipline forreporting margins; strength and allowable computation leaves live inthe structures pack.## Domain quick reference- Quantity convention: allowable and applied values are loads in newtons (N). Stresses in pascals (Pa) work identically because the margin is unitless, but a single call must never mix units: pick one unit (all N, or all Pa) and state it in the report. The Pa/MPa mix is the known bug class.- Margin of safety MS = (allowable / applied) - 1, unitless decimal.- MS >= 0 passes (allowable at least equals applied); MS < 0 fails.- Margin percent = MS * 100, in percent.- Limit margin ML = (limit_allowable / limit_applied) - 1, the limit basis check.- Example: allowable 125000 N, applied 100000 N: MS = 0.25, pass.- Example: allowable 90000 N, applied 100000 N: MS = -0.10, fail.## Workflow1. Pick the quantity and unit convention (loads in newtons), the same unit for both inputs.2. Compute the margin with margin_of_safety.3. Express it as a percent with margin_percent.4. Check the limit basis with limit_margin.5. Get the verdict with margin_verdict.6. Write the report sentence with report_margin, naming the basis (limit or ultimate).## Pitfalls- Mixing units: Pa for one input and MPa for the other. The margin formula divides one value by the other, so mixed units silently corrupt the result. Pick one unit for both inputs.- Reading a negative margin as an error: MS < 0 is a real fail verdict to report, not an exception.- Forgetting the basis: the report sentence must state limit or ultimate.- Reporting the percent margin as the decimal margin: margin_percent returns MS * 100, not MS.- Writing the margin without the verdict: the report sentence carries the margin, the basis, and the pass/fail verdict.## Behavior contract (gate 3)The margin logic is exercised by the gate 3 contract test:scripts/test_engineering_margins.py againstscripts/engineering_margins_logic.py (stdlib unittest, offline). Run:python3 scripts/test_engineering_margins.py## Compliance- Standards referenced, not reproduced: FAR-25 and CS-25 are referenced for the margin-of-safety practice; the margin formula is common structural-analysis methodology, summary-only per standards-map.yaml.- compliance: STANDARDS-REF, gated: false.

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