---

name: document-types description: 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. allowed-tools:

• Read
• Grep
• Glob

---

Mortgage Document Types

Purpose

Work with document classification in the mortgage underwriting system.

Document Type Constants

Located in internal/model/document.go:

Income Documents

Asset Documents

Credit Documents

Collateral Documents

Type Inference Logic

Located in internal/document/store.go:

Copy// 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

Copyconst (
    // ... existing types ...
    DocTypeNewType DocumentType = "new_type"
)

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

Copypatterns := 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):

Copyfunc (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

Copytype 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