Sheet Generation API

Generate CSV, Markdown, and XLSX spreadsheets from structured tabular data.

Cost: 2 credits per request

Prerequisites

You need an Iteration Layer API key. Get one at platform.iterationlayer.com — free trial credits included, no credit card required.

For full integration guidance (SDKs, auth, MCP, error handling), see the Iteration Layer Integration Guide.

API Reference

Generate CSV, Markdown, and XLSX spreadsheets from a single API call. Send column definitions and row data as structured JSON, and receive the rendered spreadsheet as base64-encoded JSON in the response.

Key Features

• Three Output Formats -- Generate CSV, Markdown tables, or XLSX from one unified input structure.
• Positional Rows -- Rows are arrays of cells matching column order. No key mapping needed.
• Cell Formatting -- Format types: text, number, decimal, currency, percentage, date, datetime, time, custom.
• Currency Support -- ISO 4217 currency codes with configurable number separator styles.
• Rich Styling -- Base styles for headers and body, with per-cell overrides for font, color, alignment, and more (XLSX).
• Custom Fonts -- Upload font files (base64-encoded) with weight and style metadata (XLSX).
• Multiple Sheets -- XLSX supports multiple worksheets. Markdown renders each sheet as a headed table. CSV supports a single sheet.
• Merged Cells -- Combine cells across rows and columns using from/to ranges on individual cells (XLSX).
• Formulas -- Any cell value starting with

  =

  is treated as a formula. Native in XLSX, server-evaluated for CSV and Markdown.

Overview

The Sheet Generation API creates spreadsheets from a JSON definition. You send a format, column definitions, row data, and optional styles, and receive the rendered spreadsheet as base64-encoded JSON.

Endpoint:

POST /sheet-generation/v1/generate

Supported output formats: CSV, Markdown, XLSX

Request Format

curl -X POST \
  https://api.iterationlayer.com/sheet-generation/v1/generate \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "format": "xlsx",
    "sheets": [
      {
        "name": "Invoices",
        "columns": [
          {
            "name": "Company",
            "width": 20
          },
          {
            "name": "Total",
            "width": 15
          }
        ],
        "rows": [
          [
            {
              "value": "Acme Corp"
            },
            {
              "value": 1500.50,
              "format": "currency",
              "currency_code": "EUR"
            }
          ]
        ]
      }
    ]
  }'

import { IterationLayer } from "iterationlayer";
const client = new IterationLayer({
  apiKey: "YOUR_API_KEY",
});

const result = await client.generateSheet({
  format: "xlsx",
  sheets: [
    {
      name: "Invoices",
      columns: [
        {
          name: "Company",
          width: 20,
        },
        {
          name: "Total",
          width: 15,
        },
      ],
      rows: [
        [
          {
            value: "Acme Corp",
          },
          {
            value: 1500.50,
            format: "currency",
            currency_code: "EUR",
          },
        ],
      ],
    },
  ],
});
// result.data.buffer is base64-encoded
// result.data.mime_type is "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"

from iterationlayer import IterationLayer
client = IterationLayer(api_key="YOUR_API_KEY")

result = client.generate_sheet(
    format="xlsx",
    sheets=[
        {
            "name": "Invoices",
            "columns": [
                {
                    "name": "Company",
                    "width": 20
                },
                {
                    "name": "Total",
                    "width": 15
                },
            ],
            "rows": [
                [
                    {
                        "value": "Acme Corp"
                    },
                    {
                        "value": 1500.50,
                        "format": "currency",
                        "currency_code": "EUR",
                    },
                ],
            ],
        },
    ],
)
# result["data"]["buffer"] is base64-encoded
# result["data"]["mime_type"] is "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"

import il "github.com/iterationlayer/sdk-go"
client := il.NewClient("YOUR_API_KEY")

result, err := client.GenerateSheet(
	il.GenerateSheetRequest{
		Format: "xlsx",
		Sheets: []il.Sheet{
			{
				Name: "Invoices",
				Columns: []il.SheetColumn{
					{
						Name:  "Company",
						Width: 20,
					},
					{
						Name:  "Total",
						Width: 15,
					},
				},
				Rows: [][]il.SheetCell{
					{
						{
							Value: "Acme Corp",
						},
						{
							Value:        1500.50,
							Format:       "currency",
							CurrencyCode: "EUR",
						},
					},
				},
			},
		},
	},
)
// result.Data.Buffer is base64-encoded
// result.Data.MimeType is "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"

{
  "success": true,
  "data": {
    "buffer": "UEsDBBQAAAAIAA...",
    "mime_type": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
  }
}

Request Structure

The top-level request has the following fields:

format

csv

markdown

xlsx

sheets

styles

fonts

webhook_url

Async Mode

Add a

webhook_url

201 Accepted

Sheets

Each sheet definition contains:

name

columns

rows

Columns

name

width

Rows and Cells

Each row is an array of cells, where each cell's position corresponds to the column at the same index. A cell can be a bare value (string, number, boolean, or null) or a structured object with formatting:

Bare value:

[
  "Acme Corp",
  1500.50
]

Structured cells with format and styles:

[
  {
    "value": "Acme Corp"
  },
  {
    "value": 1500.50,
    "format": "currency",
    "currency_code": "EUR",
    "styles": {
      "is_bold": true,
      "font_color": "#008000"
    }
  }
]

You can mix bare values and structured cells in the same row. A row may have fewer cells than columns -- trailing cells default to empty.

Cell Fields

value

=

format

text

currency_code

USD

currency

number_style

comma_period

number

decimal

currency

date_style

dd/mm/yyyy

date

datetime

time

styles

from_col

to_col

from_row

to_row

Cell Formats

text

Acme Corp

number

1,500

#,##0

decimal

1,500.50

#,##0.00

currency

$1,500.50

$#,##0.00

percentage

75.00%

0.00%

date

2026-01-15

yyyy-mm-dd

date_style

datetime

2026-01-15 10:30:00

yyyy-mm-dd hh:mm:ss

date_style

time

10:30:00

hh:mm:ss

date_style

custom

number_format

Cell Styles

Cell-level style overrides (XLSX only, ignored for CSV/Markdown):

font_family

font_size_in_pt

is_bold

is_italic

font_color

#FF0000

background_color

horizontal_alignment

left

center

right

number_format

format: "custom"

Styles

The top-level

styles

{
  "styles": {
    "header": {
      "font_family": "Helvetica",
      "font_size_in_pt": 12,
      "is_bold": true,
      "background_color": "#4472C4",
      "font_color": "#FFFFFF"
    },
    "body": {
      "font_family": "Helvetica",
      "font_size_in_pt": 11,
      "font_color": "#000000"
    }
  }
}

Header styles apply to the column header row. Body styles apply to all data cells. Per-cell

styles

Custom Fonts

Upload custom fonts as base64-encoded buffers (XLSX only). Each font definition requires a name, weight, style, and the font file data.

name

weight

thin

extralight

light

regular

medium

semibold

bold

extrabold

black

style

normal

italic

buffer

Merged Cells

Merge a range of cells by setting

from_col

to_col

from_row

to_row

value

{
  "format": "xlsx",
  "sheets": [
    {
      "name": "Report",
      "columns": [
        {
          "name": "A",
          "width": 20
        },
        {
          "name": "B",
          "width": 20
        },
        {
          "name": "C",
          "width": 20
        }
      ],
      "rows": [
        [
          {
            "value": "Summary",
            "from_col": 0,
            "to_col": 2,
            "from_row": 0,
            "to_row": 0,
            "styles": {
              "is_bold": true,
              "horizontal_alignment": "center"
            }
          }
        ],
        [
          "Detail A",
          "Detail B",
          "Detail C"
        ]
      ]
    }
  ]
}

In this example, the first row's single cell spans all three columns (columns 0 through 2). The second row has three separate cells.

Formulas

Any cell whose

value

=

{
  "format": "xlsx",
  "sheets": [
    {
      "name": "Totals",
      "columns": [
        {
          "name": "Item",
          "width": 20
        },
        {
          "name": "Amount",
          "width": 15
        }
      ],
      "rows": [
        [
          "Widget A",
          {
            "value": 100.00,
            "format": "currency"
          }
        ],
        [
          "Widget B",
          {
            "value": 250.00,
            "format": "currency"
          }
        ],
        [
          {
            "value": "Total",
            "styles": {
              "is_bold": true
            }
          },
          {
            "value": "=SUM(B2:B3)",
            "format": "currency"
          }
        ]
      ]
    }
  ]
}

For XLSX, formulas are written natively and evaluated by Excel. For CSV and Markdown, simple aggregation formulas (SUM, AVERAGE, COUNT, MIN, MAX) are evaluated server-side. Unsupported formulas are written as raw strings.

Multiple Sheets

XLSX and Markdown support multiple sheets. CSV supports only one sheet.

XLSX: Each sheet becomes a separate worksheet in the workbook.

Markdown: Each sheet is rendered as a

## Sheet Name

## Invoices

| Company | Total |
| --- | --- |
| Acme Corp | EUR 1,500.50 |

## Payments

| Date | Amount |
| --- | --- |
| 2026-01-15 | $500.00 |

CSV: If more than one sheet is provided, the API returns a 400 error.

Currency Codes

The

currency_code

currency

USD

[
  {
    "value": 1500.50,
    "format": "currency",
    "currency_code": "EUR"
  },
  {
    "value": 2400.00,
    "format": "currency",
    "currency_code": "JPY"
  },
  {
    "value": 899.99,
    "format": "currency",
    "currency_code": "GBP"
  }
]

Number Styles

The

number_style

number

decimal

currency

comma_period

comma_period

,

.

1,500.50

period_comma

.

,

1.500,50

space_comma

,

1 500,50

space_period

.

1 500.50

[
  {
    "value": 1500.50,
    "format": "decimal",
    "number_style": "period_comma"
  }
]

Date Styles

The

date_style

date

datetime

time

yyyy

2026

yy

26

mmmm

March

mmm

Mar

mm

hh

h

03

m

hh

h

3

dd

21

d

21

hh

14

h

2

ss

05

s

5

Default values if

date_style

• date

  :

  yyyy-mm-dd

• datetime

  :

  yyyy-mm-dd hh:mm:ss

• time

  :

  hh:mm:ss

[
  {
    "value": "2026-03-21",
    "format": "date",
    "date_style": "dd/mm/yyyy"
  },
  {
    "value": "2026-03-21 14:30:00",
    "format": "datetime",
    "date_style": "d mmmm yyyy hh:mm:ss"
  },
  {
    "value": "14:30:00",
    "format": "time",
    "date_style": "hh:mm"
  }
]

Feature Comparison by Format

Recipes

For complete, runnable examples see the Recipes page.

Error Responses

Links

• Integration guide
• Full documentation
• OpenAPI spec
• Browse recipes