Schematic plan

<CRITICAL-RULE> NEVER use the Read, Write, or Edit tools on KiCad files (.kicad_sch, .kicad_pcb, .kicad_sym, .kicad_mod, .kicad_pro, .kicad_prl). ALL KiCad file manipulation MUST go through the kicad MCP tools. NEVER run kicad-cli commands via Bash. If an MCP tool returns an error, try different parameters — do NOT fall back to manual file editing.

EVERY KiCad operation has a corresponding MCP tool. Do NOT claim a tool does not exist without first listing all available tools. Key tools that MUST be used instead of file writes:

• add_symbol — create custom symbol definitions in .kicad_sym files
• create_symbol_library — create new .kicad_sym library files
• create_schematic — create new .kicad_sch files
• create_project — create new .kicad_pro project files If you find yourself thinking "there's no MCP tool for this," you are wrong. Check the tool list again. </CRITICAL-RULE>

Schematic Plan

Pure planning phase — no file modifications. Only inspection MCP tools (list_lib_symbols, get_symbol_info). Note: get_symbol_pins requires a schematic with placed symbols and cannot be used during planning. Use get_symbol_info instead — it reads pin definitions directly from library files.

Inputs: specs/bom.md (validated BOM from circuit-design) Outputs: specs/schematic-plan.md (placement and wiring plan)

Response Format

When this skill activates, print exactly:

Using schematic-plan to plan placement and wiring from the validated BOM.

Then immediately proceed to the Pre-flight checks. This is a mechanical planning phase — do not ask the user what to do. Read specs/bom.md and execute the planning steps.

Report progress at natural milestones (after page size calculation, after coordinate assignment, after wiring plan). Keep status updates to one line each.

Pre-flight

1. Verify specs/bom.md exists
2. Verify BOM reviewer returned APPROVED
3. Read the BOM and count components per stage
4. If modifying an existing hierarchical schematic, run validate_hierarchy to inspect current annotation state — the plan must account for existing ref conflicts

Planning Steps

Step 1: Page Size Calculation

Count components per stage. Estimate space using spacing rules:

• Each component: ~12.7mm vertical, ~12.7mm horizontal
• Inter-stage gap: 25.4–50.8mm
• Title block: ~108x32mm at bottom-right
• Margins: 10mm all sides
• Usable area = page dimensions - margins - title block

Calculate total bounding box. Pick smallest standard page that fits. Record decision and math explicitly (show the arithmetic).

Standard page sizes (landscape):

Size	Width (mm)	Height (mm)	Usable W	Usable H
A4	297	210	179	168
A3	420	297	302	255
A2	594	420	476	378

Usable W = width - 20 (margins) - 108 (title block width near bottom-right). Usable H = height - 20 (margins) - 32 (title block height).

Step 2: Stage Layout

Assign each functional stage a bounding box on the sheet:

## Stage Layout
| Stage | Bounding Box | Components |
|-------|-------------|------------|
| Input protection | (25, 50) -> (140, 90) | J1, F1, D1, C1, C2, Q1, D3, R5 |
| Buck converter | (25, 115) -> (240, 170) | U1, C3, C4, ... |

Step 3: Component Coordinates

Assign exact (x, y) per component within its stage bounding box:

• Active component centered in stage
• Input passives to the left, output to the right
• Decoupling caps 25.4mm from their IC
• Signal flow left-to-right, voltage top-to-bottom

## Placement
| Ref | lib_id | x | y | rotation | Stage |
|-----|--------|---|---|----------|-------|
| J1 | Connector_Generic:Conn_01x02 | 25.4 | 50.8 | 0 | Input protection |

Step 4: Wiring Plan

For each net, specify tool and connections. Available tools:

• connect_pins — direct Manhattan wire between two adjacent pins
• wire_pins_to_net — connect one or more pins to a named net label

Group all pins for the same net into a single wire_pins_to_net call. Do not make separate calls for individual pins on the same net. Wiring order follows table order top-to-bottom; list power nets before signal nets.

## Wiring
| Order | Net | Tool | Pins |
|-------|-----|------|------|
| 1 | J1:1 -> F1:1 | connect_pins | Direct, adjacent |
| 2 | VIN | wire_pins_to_net | F1:2, D1:K, C1:1, C2:1, Q1:S, D3:K |
| 3 | PGND | wire_pins_to_net | J1:2, D1:A, C1:2, C2:2, R5:2 |

Step 5: No-Connect and Power Flags

List pins needing no-connect flags and nets needing PWR_FLAG.

## No-Connect Pins
| Ref | Pin | Reason |
|-----|-----|--------|
| U1  | NC  | Unused pin per datasheet |

## Power Flags
| Net | Reason |
|-----|--------|
| VOUT | Regulator output, not recognized as power source by KiCad |

Step 6: Hierarchical Sheets (if applicable)

If the design requires multiple sheets, plan sheet boundaries and hierarchical labels here.

MCP Tools for This Skill

These are the ONLY kicad MCP tools you should use during planning (inspection only — no modifications):

Symbol and footprint lookup:

• list_lib_symbols — verify symbol exists in library
• get_symbol_info — get pin names, types, and properties
• list_lib_footprints — verify footprint exists
• get_footprint_info — check pad dimensions

Schematic inspection (if schematic already exists):

• get_schematic_summary — get item counts for a sheet
• list_schematic_components — list symbols on a sheet
• list_schematic_labels — list net labels on a sheet
• list_schematic_wires — list wires on a sheet
• list_schematic_global_labels — list global labels on a sheet
• list_schematic_hierarchical_labels — list hierarchical labels on a sheet
• list_schematic_sheets — list hierarchical sheet blocks on a sheet
• list_schematic_junctions — list junctions on a sheet
• list_schematic_no_connects — list no-connect flags on a sheet
• list_schematic_bus_entries — list bus entries on a sheet
• is_root_schematic — check if a schematic is root or sub-sheet
• list_hierarchy — view the full sheet hierarchy tree
• get_sheet_info — get sheet details with pin/label matching status
• validate_hierarchy — check for orphaned labels/pins, direction mismatches, duplicate refs Run validate_hierarchy before planning to understand existing annotation state. If it reports duplicate_ref or unannotated_ref, the plan should include an annotation step.
• list_cross_sheet_nets — list all nets crossing sheet boundaries
• get_symbol_instances — list symbol instances from root schematic
• trace_hierarchical_net — trace a net across the hierarchy to understand existing cross-sheet connections before planning new ones

Do NOT use get_symbol_pins — it requires a placed schematic. Use get_symbol_info instead.

Schematic Plan Reviewer

After writing specs/schematic-plan.md, dispatch the schematic plan reviewer subagent:

Agent(
  prompt="<contents of agents/schematic-plan-reviewer.md>\n\nPlan path: <project_dir>/specs/schematic-plan.md\nBOM path: <project_dir>/specs/bom.md",
  subagent_type="general-purpose"
)

Fix any issues reported by the reviewer, update specs/schematic-plan.md, and re-dispatch until the reviewer returns APPROVED.

<HARD-GATE> User must explicitly approve the plan before schematic-design can start. "The coordinates look reasonable" is not approval — the reviewer must have returned APPROVED first. </HARD-GATE>

User rejection handling: If the user rejects the plan or requests changes (e.g., different stage layout, different page size), fix the specific issues and re-run the schematic plan reviewer.

Checklist

IMPORTANT: Use TodoWrite to create todos for EACH checklist item below.

• Verify specs/bom.md exists and is APPROVED
• Count components per stage
• Calculate page size (show arithmetic)
• Assign stage bounding boxes
• Plan exact (x, y) coordinates per component
• Plan wiring with tool selection per net
• Plan no-connect pins and power flags
• Write specs/schematic-plan.md artifact
• Dispatch schematic plan reviewer subagent
• Get user approval on plan

Rationalization Prevention

Thought	Reality
"A4 is big enough"	Show the math. Components * spacing + margins + title block.
"These coordinates look right"	Check every Y < page_height - margin, every X < page_width - margin.
"I know this pin name"	Call get_symbol_info. Don't guess pin names from memory.
"The spacing is fine"	Minimum 10.16mm vertical, 12.7mm horizontal. Measure, don't eyeball.

Your Job

1. Create directory: mkdir -p skills/schematic-plan
2. Write the file with the EXACT content above
3. Verify: frontmatter, CRITICAL-RULE, 6 planning steps, page size table, wiring batching, inspection-only tools, reviewer dispatch, HARD-GATE, rationalization table
4. Commit: git commit -m "feat: add schematic-plan skill for placement and wiring planning" (NO Co-Authored-By)