em-modeling

em-modeling is a skill for Claude Code from hdl-tools/analog-chip-design-agents. It costs 119 tokens per session (3,211 once invoked), scanned A, original, MIT.

A set of instructions for modelling the electromagnetic behaviour of an on-chip passive or antenna and preparing its model for RF circuit simulation.

In plain words
What is it for?
Use it to guide setup, geometry, meshing, solving, S-parameter extraction, model fitting, and final sign-off, including limited re-solving after failures.
Why use it?
It defines the stages and checks needed to produce a converged, passive model rather than relying on an unchecked simulation result.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Part of the analog-design-em plugin — 1 skill, 1 agent shipped together

Good fit Use it to guide setup, geometry, meshing, solving, S-parameter extraction, model fitting, and final sign-off, including limited re-solving after failures.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/hdl-tools/analog-chip-design-agents/em-modeling
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 hdl-tools/analog-chip-design-agents --skill em-modeling
Clone the repo
git clone --depth 1 https://github.com/hdl-tools/analog-chip-design-agents

Made for: Claude Code.

Or install analog-design-em, the plugin that ships this one along with the rest of its 1 skill, 1 agent.

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 em-modeling

README.md
[![agentmods](https://agentmods.dev/badge/skills/hdl-tools/analog-chip-design-agents/em-modeling/github.svg)](https://agentmods.dev/skills/hdl-tools/analog-chip-design-agents/em-modeling)
Your own site
<a href="https://agentmods.dev/skills/hdl-tools/analog-chip-design-agents/em-modeling"><img src="https://agentmods.dev/badge/skills/hdl-tools/analog-chip-design-agents/em-modeling/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 em-modeling

Your own site · 80×15
<a href="https://agentmods.dev/skills/hdl-tools/analog-chip-design-agents/em-modeling"><img src="https://agentmods.dev/badge/skills/hdl-tools/analog-chip-design-agents/em-modeling.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 119 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,211 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.
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 $0.00119 $0.03211
Opus 5 $0.00060 $0.01605
Sonnet 5 $0.00024 $0.00642
Haiku 4.5 $0.00012 $0.00321

Measured 10d ago against content hash e80284b477bd, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

em-modeling 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 10d ago.

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.

plugins/em/skills/em-modeling/SKILL.md · 298 lines

How it starts

The opening of the file, as written. The whole thing — 298 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill: EM Modeling

Invocation

  • If invoked by a user presenting an EM-modeling task: immediately spawn the analog-chip-design-agents:em-modeling-orchestrator agent and pass the full user request and any available context. Do not execute stages directly.
  • If invoked by the em-modeling-orchestrator mid-flow (including fix_request re-solves): do not spawn a new agent. Treat this file as read-only — return the requested stage rules, sign-off criteria, or loop-back guidance.

Spawning the orchestrator from within an active orchestrator run causes recursive delegation and must never happen.

Pre-run Context

Before executing or advising on any stage, read the following if they exist:

  1. memory/em/knowledge.md — known meshing recipes, passivity/fit fixes, de-embedding patterns, solver-selection rules, and PDK/tool quirks. Incorporate its guidance into every stage.
  2. memory/em/run_state.md — current run identity for resume-after-interruption.

Purpose

Solve the electromagnetics of an on-chip passive or antenna, extract a converged, passive S-parameter model, and fit a lumped equivalent for circuit-level RF simulation. Seven stages with explicit QoR gates. EM modeling is a data-dependency producer and a cross-domain servicer: it writes a Touchstone S-parameter model + fitted lumped model into design_state.em that rf-design reads as a passive input. Its loop-backs are stage-local (passivity/fit fail → meshing / geometry_definition, max 2×); a fundamental geometry/stack-up gap escalates to the user. EM modeling does not open fix_requests, but it services rf-design-raised ones (route_to: em-modeling): when dispatched with a fix_request.id it re-solves the passive toward a higher-Q / higher-SRF target and closes the entry with a circuit_response so the pipeline-orchestrator re-validates RF.


Supported EDA Tools

Open-Source

  • openEMS (openEMS) — FDTD full-wave solver (distributed passives, antennas, mmWave)
  • FastHenry (fasthenry) / FastCap (fastcap) — quasi-static RL / C field solvers
  • gmsh (gmsh) — mesh generation
  • scikit-rf (Python skrf) — passivity / causality checks, fitting, de-embedding

Read the full file on GitHub · 298 lines

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. 10d ago First seen · 298 lines · 119 tokens per session scan A e80284b477bd

Subscribe to this mod's changes

em-modeling is a skill published in the GitHub repository hdl-tools/analog-chip-design-agents (22 stars, last pushed 3mo ago), licensed MIT. It adds 119 tokens to every session and 3,211 once invoked, about $0.0006 per session on Opus 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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