microcap-mcp 0.1.0

MCP server exposing Micro-Cap 12 circuit simulation to LLM agents

microcap-mcp

An AI agent builds, simulates and draws analog circuits in Micro-Cap 12.

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_{The schematic is drawn by the server itself (1:1 with Micro-Cap, operating point overlaid) · the plot is computed by Micro-Cap}

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Works through Micro-Cap's own batch mode (MC12 @batch.bat) — headless, no GUI automation, no modification of the program.

What it does

🔧 Builds circuits from scratch — 8 stage generators (common-emitter, follower, MOSFET, differential pair, current mirror, cascode, op-amp, RLC) with automatic biasing. Each is checked against theory: gain, operating point, resonance.

📊 Simulates — transient / AC / DC / distortion / stability, operating point, sweeps. Complex output as {re, im}, solver diagnostics.

🎨 Draws — renders a .CIR to SVG 1:1 with Micro-Cap: the native symbols from MC's shape library, the dot grid, every rotation and reflection, the label layout. Overlays operating-point voltages. MC's /IC can't export a drawing in batch — this can.

Install

Needs Windows, Python 3.11+ and an installed copy of Micro-Cap 12 (freeware). Nothing to clone — point your MCP client at it and uvx fetches the package:

{
  "mcpServers": {
    "microcap": {
      "command": "uvx",
      "args": ["microcap-mcp"],
      "env": { "MICROCAP_HOME": "E:/Tools/MC12" }   // only if the scan misses it
    }
  }
}

The driver looks for Micro-Cap in the usual places; set MICROCAP_HOME to the folder holding mc12_64.exe if yours lives elsewhere.

From source instead

git clone https://github.com/monoxide-xen/microcap-mcp
cd microcap-mcp
uv sync

{
  "mcpServers": {
    "microcap": {
      "command": "uv",
      "args": ["--directory", "C:/path/to/microcap-mcp", "run", "microcap-mcp"]
    }
  }
}

Tools

Tool	Does
simulate · sweep · plot	run a SPICE netlist, sweep a .DEFINE, render a JPEG plot
generate_transistor_amplifier · _emitter_follower · _mosfet_amplifier	BJT / MOSFET stages, auto-biased to a mid-supply operating point
generate_differential_pair · _current_mirror · _cascode · _amplifier	differential pair, current mirror, cascode, op-amp amplifier
generate_schematic	a source + R/C/L in series and parallel (RC/RL/RLC, dividers, tanks)
simulate_schematic · plot_schematic	run / plot an arbitrary .CIR
draw_schematic · annotate_schematic	render a .CIR to SVG (1:1 with MC) · with the operating point on the drawing
simulate_example · search_examples · get_example · describe_example · list_domains	the ~490 reference circuits shipped with MC: search, source, analyses

Plus resources microcap://guide and microcap://domains and an analyse_circuit prompt — so the agent doesn't let Micro-Cap silently mislead it.

Tests

uv run pytest        # 138 unit with no Micro-Cap; +30 integration against physics (needs MC)

Without Micro-Cap the integration tests skip, so CI stays green.

How it works

• Micro-Cap notes — behaviour that is not in the manual, and in places contradicts it.
• eval/harness.py — runs all ~490 shipped circuits and buckets the failures by cause (88% answer today).

Licence

MIT for the code in this repository. Micro-Cap 12 belongs to Spectrum Software — not included, redistributed or modified: this uses its documented CLI.