claude-kicad-helper

A command-line query tool for KiCad project files, designed to extract focused, readable information from files that are otherwise too large to work with directly.

Why this exists

KiCad stores schematics (.kicad_sch) and PCB layouts (.kicad_pcb) as S-expression trees that easily run to thousands of lines. Most of that bulk is graphical metadata — line coordinates, font sizes, courtyard polygons — that is irrelevant when you want to answer questions like:

• What components are on this board and what are their values?
• Which nets exist in this schematic?
• What copper traces physically connect to pin 1 of R5?

kicad-query.mjs parses the file, extracts structured data, and prints only what was asked for — either as a human-readable table or as JSON for programmatic/LLM consumption.

Architecture

tokenize(text)          generic S-expression tokenizer
parse_sexp(text)        builds { tag, items[] } tree
        │
        ▼
run_query(ext, query, root, args)   file-type + query dispatch → plain data object
        │
        ├── render_human(ext, query, data)   formatted tables for terminal
        └── render_json(data)                JSON.stringify for LLM / scripts

Query functions are pure data transformers — no I/O, no format awareness. Adding a new output format only requires a new renderer.

Installation

npm install -g git+https://gitea.efforting.tech/mikael-lovqvists-claude-agent/claude-kicad-helper.git

This installs the kicad-query command globally. Requires Node.js 18+, no other dependencies.

Usage

kicad-query [--format=json] <file> <query> [args...]

Or without installing, directly via node:

node kicad-query.mjs [--format=json] <file> <query> [args...]

Queries

Schematic (.kicad_sch)

Query	Description
summary	Component counts, wire count, libraries used
components	Table of all placed components (ref, value, footprint)
components ref=U*	Filter by reference glob
components value=100nF	Filter by value glob
component U1	All properties and pins of one component
nets	All net names (local labels, global labels, power nets)

PCB (.kicad_pcb)

Query	Description
summary	Net, footprint, segment, via, zone counts
nets	All nets with their numeric IDs
net GND	Which pads are connected to a named net
footprints	Table of all footprints
footprint R5	Position, layer, value, pad→net table for one footprint
traces R5 1	BFS through segments and vias from pad 1 of R5

Project (.kicad_pro)

Query	Description
summary	Filename, version, min clearance, section list

Generic (any file)

Query	Description
tags	All S-expression tag names sorted by frequency — useful for exploration
raw <tag>	Dump all nodes with a given tag name

---

Examples — human output

$ node kicad-query.mjs sketch.kicad_sch summary
=== Schematic Summary ===
Components   : 26
Power symbols: 14
Net labels   : 0
Global labels: 16
Wires        : 102

Libraries:
  Amplifier_Operational: 1
  Connector: 4
  Device: 16
  Mechanical: 4

$ node kicad-query.mjs sketch.kicad_sch components
Reference  Value             Library:Symbol               Footprint
---------  -----             --------------               ---------
C1         100 nF            Device:C                     Capacitor_SMD:C_0603_1608Metric
C5         100 µF            Device:C_Polarized           Capacitor_SMD:CP_Elec_6.3x4.5
R4         100 mΩ            Device:R                     Resistor_SMD:R_1206_3216Metric
U1         LM358             Amplifier_Operational:LM358  Package_SO:SO-8_3.9x4.9mm_P1.27mm
...

$ node kicad-query.mjs sketch.kicad_sch nets
=== Net Names (10 total) ===
  BIAS  [global]
  Current Measurement  [global]
  GND  [power]
  SUPPLY  [global]
  VDD  [power]
  Voltage Reference  [global]
  ...

$ node kicad-query.mjs sketch.kicad_pcb traces R5 1
=== Traces from R5 pad 1 ===
Net        : Current Reference (id=12)
Position   : (148.645, 64.350)
Pad layers : F.Cu

Layer B.Cu — 2 segment(s):
  From (x, y)           To (x, y)             Width
  (153.162,  74.168)  → (153.670,  73.660)    0.4mm
  (153.162,  81.026)  → (153.162,  74.168)    0.4mm

Layer F.Cu — 9 segment(s):
  ...

Vias (2):
  (153.670, 73.660)  F.Cu ↔ B.Cu
  (153.162, 81.026)  F.Cu ↔ B.Cu

---

Examples — JSON / LLM output

Add --format=json before the filename. All queries produce the same data; only the presentation changes.

$ node kicad-query.mjs --format=json sketch.kicad_sch components
{
  "components": [
    {
      "ref": "C1",
      "value": "100 nF",
      "footprint": "Capacitor_SMD:C_0603_1608Metric",
      "lib_id": "Device:C",
      "datasheet": "~",
      "dnp": false
    },
    ...
  ]
}

$ node kicad-query.mjs --format=json sketch.kicad_pcb traces R5 1
{
  "ref": "R5",
  "pad": "1",
  "net": { "id": 12, "name": "Current Reference" },
  "position": { "x": 148.645, "y": 64.35 },
  "pad_layers": ["F.Cu"],
  "traces": [
    { "layer": "F.Cu", "start": { "x": 149.225, "y": 64.35 }, "end": { "x": 148.645, "y": 64.35 }, "width": 0.4 },
    ...
  ],
  "vias": [
    { "position": { "x": 153.670, "y": 73.660 }, "layers": ["F.Cu", "B.Cu"] }
  ]
}

When feeding KiCad data to an LLM, prefer --format=json with targeted queries over pasting raw file contents. A 6000-line schematic collapses to a few hundred bytes of component and net data.