Detects .pen files and pencil-plan.md in .moai/design/, loads Pencil MCP, executes batch operations with layout verification, archives screenshots. Invoked from /moai design Phase B2.6 when preconditions are met.
Detects .pen files and pencil-plan.md in .moai/design/, loads Pencil MCP, executes batch operations with layout verification, archives screenshots. Invoked from /moai design Phase B2.6 when preconditions are met.
Pencil MCP integration skill for the /moai design Phase B2.6 workflow. Detects .pen files and pencil-plan.md, loads Pencil MCP tools via ToolSearch, parses DSL batch operations, executes them with layout verification, archives screenshots, and produces a run summary report.
This skill is invoked only when Phase B2.6 file/folder preconditions are satisfied. It is never invoked directly by the user.
Quick Reference
Entry Conditions (REQ-PENCIL-001)
Phase B2.6 checks these file/folder preconditions before invoking this skill:
.moai/design/pencil-plan.md exists.
At least one .pen file exists in .moai/design/ or project root.
If either condition fails, Phase B2.6 skips gracefully without error and proceeds to Phase B3 (REQ-PENCIL-002). This skill is not invoked in that case.
When both conditions are met, this skill is invoked and must complete (success or structured error) before Phase B3 begins (REQ-PENCIL-003).
ToolSearch with query "mcp__pencil" returns no matching tool schemas at runtime (REQ-PENCIL-013).
Return this code to the orchestrator. Phase B2.6 ends; orchestrator proceeds to Phase B3. Include Pencil MCP setup guidance: "Install and enable the Pencil MCP server. See Pencil MCP documentation for setup instructions."
PENCIL_CONNECTION_FAILED
mcp__pencil__get_editor_state returns a connection failure, or the open document name does not match the detected .pen file (REQ-PENCIL-006).
Return this code to the orchestrator. Phase B2.6 ends; orchestrator proceeds to Phase B3. Include user action guidance: "Restart Claude Desktop or open the correct .pen file in Pencil before retrying."
PENCIL_PLAN_SYNTAX_ERROR
pencil-plan.md contains tokens outside the DSL Grammar. Collect ALL errors before returning — do not halt on the first (REQ-PENCIL-016).
Return this code with a list of {line_number, offending_text} entries covering all discovered syntax errors. Halt execution. User must correct pencil-plan.md and re-run.
PENCIL_BATCH_FAILED
mcp__pencil__batch_design fails on the initial attempt AND the single retry (total 2 attempts) for a given batch (REQ-PENCIL-015).
Return this code with the failing batch index. Halt further batch execution. User must investigate Pencil state and re-run.
Implementation Guide
Step 1: ToolSearch Preloading (REQ-PENCIL-004)
Before issuing any mcp__pencil__* call, invoke ToolSearch:
ToolSearch(query="mcp__pencil")
If ToolSearch returns no matching tool schemas, return PENCIL_MCP_UNAVAILABLE immediately. Do not attempt any mcp__pencil__* calls.
If ToolSearch returns one or more matching schemas, proceed to Step 2.
Step 2: Editor State Verification (REQ-PENCIL-005)
Identify the .pen file detected by Phase B2.6 precondition check (the file found in .moai/design/ or project root).
Call mcp__pencil__get_editor_state and inspect the response:
If the response references the expected .pen file name: proceed to Step 3.
If the response indicates a connection failure or references a different document: return PENCIL_CONNECTION_FAILED with recovery guidance. Do not proceed.
parentId, nodeId are double-quoted string literals.
index is a non-negative integer.
{...props} is a JSON-serializable object literal per Pencil's batch_design schema.
Line comments (// ...) and block comments (/* ... */) are permitted and ignored.
Batch boundaries are delimited by ## Batch <N> Markdown headings (N is a positive integer starting from 1).
Each operation occupies exactly one line.
Any token that does not match I(...), M(...), R(...), a comment, or a batch heading is a syntax error.
Syntax error collection (REQ-PENCIL-016): Scan the entire file before returning. Collect every line containing an unrecognized token as {line_number, offending_text}. Do not halt on the first error. If any syntax errors are collected, return PENCIL_PLAN_SYNTAX_ERROR with the complete list.
Batch ordering (REQ-PENCIL-007): Extract batches in declaration order (Batch 1 through Batch N). Preserve this order in execution.
Step 4: Sub-batch Splitting (REQ-PENCIL-008)
For each parsed batch, if the number of operations exceeds 25:
Split into sub-batches of at most 25 operations each.
Preserve the original operation order across sub-batches.
Example: 30 operations → sub-batch A (ops 1-25) + sub-batch B (ops 26-30).
Sub-batches from the same batch are executed sequentially before moving to the next batch.
After all batches complete, list all files in .moai/design/screenshots/ matching the pattern frame-*-*.png.
Sort by filename (ISO8601 timestamp ensures chronological order). Keep the 5 most recent files. Delete any older files using the Write tool (overwrite with empty is insufficient; use Bash if needed to remove files).
Step 7: Summary Report (REQ-PENCIL-012)
Write a summary report to:
.moai/design/pencil-run-<ISO8601-timestamp>.md
The report must contain these sections:
# Pencil Run — <ISO8601-timestamp>## Applied Batches<listeachbatch:batchnumber, operationcount, sub-batchcountifsplit>## Screenshots Saved<listeachscreenshotpathsavedduringthisrun>## Warnings<listanynon-fatalwarningscollectedduringexecution, or "None">
Advanced Patterns
Partial pencil-plan.md Structures
If pencil-plan.md contains batch headings with no operations between them, treat the batch as empty and skip it (emit no batch_design call, no TaskUpdate for that batch). Do not treat an empty batch as a syntax error.
Connection Recovery
If get_editor_state indicates the Pencil app is not open (rather than a document mismatch), return PENCIL_CONNECTION_FAILED with specific guidance: "Open Pencil and load the .pen file before retrying."
Large pencil-plan.md Files
Files with many batches (> 10) will generate many TaskUpdate events. This is expected and intentional per REQ-PENCIL-014 — it allows users to monitor long-running Pencil sessions and prevents timeout confusion.
Works Well With
/moai design Phase B2.6: The only orchestrator that invokes this skill.
moai-workflow-design-context: Provides context about .moai/design/ contents before this skill runs (Phase B2.5).
moai-workflow-gan-loop: Receives Pencil wireframe artifacts for quality evaluation in Phase C.
REQ coverage: REQ-PENCIL-001 through REQ-PENCIL-016
SPEC: SPEC-DESIGN-PENCIL-001 v0.2.0
Version: 1.0.0
