Agent skill

document-types

Understand and work with mortgage document types and classification. Use when asking about document types, adding new document support, debugging classification, or understanding what DocType constants mean.

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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/development/document-types

SKILL.md

Mortgage Document Types

Purpose

Work with document classification in the mortgage underwriting system.

Document Type Constants

Located in internal/model/document.go:

Income Documents

Constant Description Filename Patterns
DocTypeW2 W-2 wage statements *w2*, *w-2*
DocType1099 1099 contractor income *1099*
DocTypePaystub Pay stubs/earnings *paystub*, *pay_stub*, *pay-stub*, *earnings*
DocTypeTaxReturn Tax returns (1040) *tax*, *1040*
DocTypeProfitLoss P&L statements *profit*, *p&l*, *pnl*
DocTypeEmploymentLetter Employment verification *employment*, *verification*

Asset Documents

Constant Description Filename Patterns
DocTypeBankStatement Bank statements *bank*
DocTypeAssetStatement General assets *asset*
DocTypeRetirementStmt 401k/IRA statements *retirement*, *401k*, *ira*
DocTypeGiftLetter Gift fund letters *gift*

Credit Documents

Constant Description Filename Patterns
DocTypeCreditReport Credit bureau reports *credit*
DocTypeDebtPayoff Debt payoff letters *payoff*, *debt*

Collateral Documents

Constant Description Filename Patterns
DocTypeAppraisal Property appraisals *appraisal*
DocTypePurchaseContract Purchase agreements *purchase*, *contract*
DocTypeTitleReport Title reports *title*
DocTypePropertyInsurance Hazard insurance *insurance*, *hazard*, *homeowner*

Type Inference Logic

Located in internal/document/store.go:

go
// Files are classified by checking if filename contains pattern
lower := strings.ToLower(filepath.Base(path))
for pattern, docType := range patterns {
    if strings.Contains(lower, pattern) {
        return docType
    }
}

Adding a New Document Type

Step 1: Add constant to internal/model/document.go

go
const (
    // ... existing types ...
    DocTypeNewType DocumentType = "new_type"
)

Step 2: Add pattern to internal/document/store.go

go
patterns := map[string]model.DocumentType{
    // ... existing patterns ...
    "new_pattern": model.DocTypeNewType,
}

Step 3: Add to agent's document lists

In the relevant agent (e.g., internal/agent/income/income.go):

go
func (a *Agent) RequiredDocuments() []model.DocumentType {
    return []model.DocumentType{
        model.DocTypeW2,
        model.DocTypeNewType,  // Add here
    }
}

Step 4: Update prompts

Update the agent's prompt to describe how to handle the new document type.

Document Structure

go
type Document struct {
    ID            string            // Hash-based unique ID
    ApplicationID string            // Loan application ID
    Type          DocumentType      // One of the DocType* constants
    FileName      string            // Original filename
    MimeType      string            // application/pdf, image/png, etc.
    FilePath      string            // Local filesystem path
    GeminiURI     string            // Cached Gemini File API URI
    UploadedAt    time.Time
    BorrowerID    string
    Year          int               // Tax year for tax docs
    Period        string            // Pay period for paystubs
    Metadata      map[string]string // Additional metadata
}

Supported MIME Types

From internal/document/store.go:MimeTypeFromExtension:

  • .pdf -> application/pdf
  • .png -> image/png
  • .jpg, .jpeg -> image/jpeg
  • .gif -> image/gif
  • .webp -> image/webp

Related Files

  • internal/model/document.go - Type definitions
  • internal/document/store.go - Loading and type inference
  • cmd/underwriter/main.go - CLI type inference

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