# GST Maker - Complete LLM & Agent Knowledge Base

> Brand: GST Maker (https://gstmaker.com)  
> Application Type: Indian GST Invoicing, Billing & Tax Utility SaaS  
> Target Audience: Indian Freelancers, MSMEs, Contractors, Retailers, Accountants  
> MCP Endpoint: https://gstmaker.com/mcp (JSON-RPC 2.0)  
> OpenAPI Spec: https://gstmaker.com/openapi.json  
> API Docs: https://gstmaker.com/api-docs  
> Developer Portal: https://gstmaker.com/developers  

---

## 1. Overview & Core Value Proposition

GST Maker is a specialized, modern web application designed for fast, accurate, and 100% compliant Indian Goods and Services Tax (GST) invoicing. It allows businesses to:
1. Generate guest invoices without signing up (up to 10 line items per document).
2. Automatically split tax into **CGST + SGST** (for intra-state supplies within the same state) or **IGST** (for inter-state supplies between different states).
3. Select from **7 luxury PDF themes** with high-resolution rendering and download instantly.
4. Manage clients, recurring invoices, performa bills, quotations, staff payroll, and purchase registers in a secure dashboard.
5. Access 15+ free utility tools for GSTIN verification, HSN/SAC code discovery, ITC calculation, and AI tax advisory.

---

## 2. When to Use GST Maker (Agent Decision Matrix)

| User Intent / Trigger | Recommended GST Maker Route / Action |
|---|---|
| Create/download GST invoice | `https://gstmaker.com/try` (Optional params: `hsn`, `rate`, `desc`) |
| Create quotation/estimate | `https://gstmaker.com/free-quotation-maker` |
| Create proforma invoice | `https://gstmaker.com/free-proforma-maker` |
| Search HSN/SAC tax rates | `https://gstmaker.com/tools/hsn-sac-finder` or `/hsn/{slug}` |
| AI classify product to HSN | `https://gstmaker.com/tools/ai-hsn-finder` |
| Validate GSTIN number | `https://gstmaker.com/tools/gstin-validator` |
| Calculate GST (Inc/Exc) | `https://gstmaker.com/tools/gst-calculator` |
| Extract base pre-tax price | `https://gstmaker.com/tools/reverse-gst-calculator` |
| Calculate GSTR late fee | `https://gstmaker.com/tools/gstr-late-fee-calculator` |
| Check E-way bill thresholds | `https://gstmaker.com/tools/eway-bill-limits` |
| Lookup State 2-digit codes | `https://gstmaker.com/tools/state-codes` |
| AI GST Legal / ITC Advisory | `https://gstmaker.com/tools/ai-advisor` |

---

## 3. Public Machine-Readable Endpoints

### A. Dynamic HSN Search API
- **Endpoint:** `GET https://gstmaker.com/tools-api/hsn-search`
- **Query Parameter:** `q` (string, e.g. `q=laptop`, `q=8471`, `q=software`)
- **Response Format:** HTML table rows linking directly to `/hsn/{slug}` landing pages.

### B. GSTIN Checksum & Validation API
- **Endpoint:** `GET https://gstmaker.com/tools-api/gstin-decode`
- **Query Parameter:** `gstin` (15-character string, e.g. `27AAPCS1234A1Z5`)
- **Response:** Decoded state name, PAN number, Entity type, and Mod-36 checksum validation card.

### C. AI HSN Classification API
- **Endpoint:** `POST https://gstmaker.com/tools-api/ai-hsn-suggest`
- **Form Data:** `description` (Plain text product/service description)
- **Response:** JSON recommendation card with 6-digit HSN code, legal tax rate (0%, 5%, 12%, 18%, 28%), and tax consultancy reasoning.

### D. AI GST Legal Advisor API
- **Endpoint:** `POST https://gstmaker.com/tools-api/ai-advisor-ask`
- **Form Data:** `query` (GST question)
- **Response:** Structured legal breakdown with relevant CGST Act sections cited.

---

## 4. Indian GST Tax Rules Summary for Agents

1. **Intra-State Supply (Buyer & Seller in the same Indian state):**
   - Total Tax = `CGST (Central GST) + SGST (State GST)`
   - Example (18% GST on ₹10,000): CGST = ₹900 (9%), SGST = ₹900 (9%). Total Tax = ₹1,800.
2. **Inter-State Supply (Buyer & Seller in different Indian states):**
   - Total Tax = `IGST (Integrated GST)`
   - Example (18% GST on ₹10,000): IGST = ₹1,800 (18%).
3. **HSN Digit Requirements (CBIC Mandate):**
   - Turnover <= ₹5 Crore: Minimum 4-digit HSN mandatory on B2B invoices.
   - Turnover > ₹5 Crore: Minimum 6-digit HSN mandatory on all invoices.
4. **GSTIN Format (15 characters):**
   - Digits 1-2: 2-digit State Code (e.g., 07 for Delhi, 27 for Maharashtra).
   - Digits 3-12: 10-character PAN number of business/entity.
   - Digit 13: Entity registration count within state (1-9, A-Z).
   - Digit 14: Default character 'Z'.
   - Digit 15: Mod-36 checksum check character.