drawing-titleblock-page

name	drawing-titleblock-page
description	Per-page titleblock extraction from drawing sheets using four corner crops and a full-page thumbnail; emits a governed sheet-inventory stub.
compatibility	Chirality TASK; dispatched by DRAWING_EXTRACT for DRAWING_SET/titleblock_index
metadata	{"chirality-skill-version":"1","chirality-task-profile":"NONE"}

SKILL - drawing-titleblock-page

Purpose

Extract titleblock metadata from one drawing page for the DRAWING_SET/titleblock_index workflow. This is a bounded per-page visual extraction skill. It does not inventory a full PDF, choose downstream page scope, or accept drawing-family classifications.

The output is a single markdown stub with YAML frontmatter and a one-row findings table.

Suitable agent shells

• TASK in generic shell mode, spawned by the DRAWING_EXTRACT orchestrator.

Inputs

Required

• RuntimeOverrides.SOURCE_PDF_NAME - source PDF basename.
• RuntimeOverrides.PAGE_NUM - 1-indexed page number.
• RuntimeOverrides.TOTAL_PAGES - total pages in the PDF.
• RuntimeOverrides.CORNER_CROP_PATHS - paths for tl, tr, bl, and br titleblock crops.
• RuntimeOverrides.THUMBNAIL_PATH - low-resolution full-page thumbnail.
• RuntimeOverrides.OUTPUT_PATH - path for the output markdown stub.
• RuntimeOverrides.CORNER_CROP_GEOMETRY - width_ratio and height_ratio used for the crops.

Runtime overrides

Key	Meaning	Default	Allowed values
SOURCE_PDF_NAME	PDF basename for provenance	Required	String
PAGE_NUM	Page number	Required	Positive integer
TOTAL_PAGES	Total pages	Required	Positive integer
CORNER_CROP_PATHS	Four corner crop paths keyed by tl,tr,bl,br	Required	Existing image paths
THUMBNAIL_PATH	Full-page thumbnail path	Required	Existing image path
OUTPUT_PATH	Stub output path	Required	.md file path
CORNER_CROP_GEOMETRY	Crop ratios	Required	width_ratio, height_ratio

Tool usage

No deterministic tools are invoked by this skill. The parent orchestrator prepares crops, validates stubs, and assembles the index.

Method

1. Validate that all required image paths and OUTPUT_PATH are present.
2. Read the full-page thumbnail to understand page orientation and whether a titleblock is present.
3. Read all four corner crops and identify the titleblock corner.
4. Extract visible metadata:
   • dwg_no
   • sheet_no
   • sheet_title
   • revision
   • area_or_module
   • drawing_family_proposal
   • titleblock_corner
   • confidence
5. If no titleblock is visible, emit NO_TITLEBLOCK with finding_count: 0.
6. Write exactly one markdown stub at OUTPUT_PATH.

Drawing-family proposal

drawing_family_proposal is not authoritative. It is a proposal for the human to review during scope acceptance. Use one of:

• PFD
• P_AND_ID
• ISOMETRIC
• GA
• OTHER
• REFERENCE_OR_LEGEND
• TBD

No-invention rule

Unreadable fields are TBD. Do not infer a drawing number or sheet number from surrounding page order. Do not convert a proposal into final operator scope.

Output format

Every stub begins with YAML frontmatter:

---
drawing_type: DRAWING_SET
extraction_target: titleblock_index
source_pdf: <SOURCE_PDF_NAME>
source_page: <PAGE_NUM>
corner_crop_geometry:
  width_ratio: 0.25
  height_ratio: 0.25
status: SUCCESS | NO_TITLEBLOCK | FAILED | FAILED_INPUTS
finding_count: 0 | 1
---

The body table columns are:

dwg_no | sheet_no | sheet_title | revision | area_or_module | drawing_family_proposal | titleblock_corner | confidence

confidence is high, medium, or low.

Outputs

• Exactly one markdown stub at OUTPUT_PATH.
• Structured return values: RUN_STATUS, PAGE_NUM, DWG_NO, DRAWING_FAMILY_PROPOSAL, CONFIDENCE.

Non-negotiable constraints

• One invocation handles one page.
• The skill reads only declared crop and thumbnail images.
• The skill writes only OUTPUT_PATH.
• drawing_family_proposal is always a proposal.
• Unknown or unreadable fields are TBD.
• NO_TITLEBLOCK is a valid non-error outcome.

QA expectations

• Output file exists at OUTPUT_PATH.
• Frontmatter matches the run parameters.
• finding_count=1 only when the body row contains a detected titleblock.
• finding_count=0 for NO_TITLEBLOCK.
• confidence is one of high, medium, low.
• Table columns match the canonical schema.