neqsim-api-patterns

neqsim-api-patterns is a skill for Claude Code, Codex from equinor/neqsim. It costs 78 tokens per session (16,957 once invoked), scanned A, original, Apache-2.0.

A code reference for using NeqSim, a Java and Python library for thermodynamic calculations, process simulation, and property retrieval.

In plain words
What is it for?
Use it when writing Java or Python code for NeqSim, including equations of state, fluid setup, flash calculations, property access, and process equipment.
Why use it?
It helps developers choose the right NeqSim API, create fluids, perform calculations, and handle units without guessing from unfamiliar interfaces.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions AGENTS.md.

Good fit Use it when writing Java or Python code for NeqSim, including equations of state, fluid setup, flash calculations, property access, and process equipment.

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Install with agentmods
npx agentmods add skills/equinor/neqsim/neqsim-api-patterns
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add equinor/neqsim --skill neqsim-api-patterns
Clone the repo
git clone --depth 1 https://github.com/equinor/neqsim

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for neqsim-api-patterns

README.md
[![agentmods](https://agentmods.dev/badge/skills/equinor/neqsim/neqsim-api-patterns/github.svg)](https://agentmods.dev/skills/equinor/neqsim/neqsim-api-patterns)
Your own site
<a href="https://agentmods.dev/skills/equinor/neqsim/neqsim-api-patterns"><img src="https://agentmods.dev/badge/skills/equinor/neqsim/neqsim-api-patterns/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for neqsim-api-patterns

Your own site · 80×15
<a href="https://agentmods.dev/skills/equinor/neqsim/neqsim-api-patterns"><img src="https://agentmods.dev/badge/skills/equinor/neqsim/neqsim-api-patterns.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 16,957 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00078 $0.16957
Opus 5.5 $0.00031 $0.06783
Sonnet 5.5 $0.00016 $0.03391
Haiku 4.5 $0.00008 $0.01696

Measured today against content hash 60e5fbdd462f, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

neqsim-api-patterns scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.github/skills/neqsim-api-patterns/SKILL.md · 1,496 lines

How it starts

The opening of the file, as written. The whole thing — 1,496 lines — stays where its author put it; the contents beside it link to each section on GitHub.

NeqSim API Patterns

Copy-paste reference for common NeqSim operations. All Java code must be Java 8 compatible.

Use progressive disclosure: search headings and read only the task-relevant section. For property-model selection, diffusion or gas-oil-water interfacial tension, read references/physical-properties.md and its tested guides. For black-oil tables, conversion and reservoir export, use docs/blackoil/README.md and the pvt-simulation agent. For APIs absent from this recipe list, follow source/runtime discovery.

MCP server vs. Python/Java API — which to use

Default policy: MCP first. For any single calculation, always check whether a NeqSim MCP tool (mcp_neqsim_*) already covers it before writing Python or Java. Only drop to code when MCP genuinely cannot do the job. Concretely:

  1. Curated tool exists (runFlash, runProcess, runPVT, getPhaseEnvelope, sizeEquipment, calculateStandard, runFlowAssurance, runBatch, ...) → use it directly. Confirm field names with getSchema/validateInput first.
  2. No curated tool, but it might still be reachable → use runCapability (search → inspectApi → invoke) before writing any code.
  3. runCapability reports inspect-only, or the task needs loops/plotting/ state/notebooks/reports → fall back to the Python API (import neqsim) or Java in a checkout. This is the only reason to write code for a calculation MCP already exposes.
  4. NeqSim itself lacks the capability (not a packaging gap, an engine gap) → implement it in Java with tests (spotless:apply) rather than working around it with ad-hoc Python; see neqsim-troubleshooting and the continuous-improvement rule in AGENTS.md.

Both the MCP tools and the Python/Java API call the same NeqSim engine — the difference is packaging, not physics — but MCP additionally gives a stable JSON contract, schema validation, and provenance/quality-gate info (EOS, convergence, benchmark trust, standards) for free.

Read the full file on GitHub · 1,496 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. today Changed · +11 lines · +18 tokens per session 60e5fbdd462f
  2. 12d ago Changed · +29 lines c034ba7a5bd9
  3. 1mo ago Changed · +39 lines d01e72356eed
  4. 1mo ago Changed · +21 lines 045ad05872c6
  5. 1mo ago Changed · +12 lines 1300cda73a77
  6. 1mo ago Changed · +9 lines b15ede74865f
  7. 1mo ago Changed · +43 lines f6279b6157e5
  8. 1mo ago First seen · 1,332 lines · 60 tokens per session scan A ccb110e57ed2

Subscribe to this mod's changes

neqsim-api-patterns is a skill published in the GitHub repository equinor/neqsim (158 stars, last pushed today), licensed Apache-2.0. It adds 78 tokens to every session and 16,957 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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