NGT API

The NGT API turns a plain-English prompt into a complete document specification and renders each section as pixel-perfect SVG. Built on Claude Sonnet (structure) and Claude Haiku (per-element rendering).

Base URL: https://nextgentext.online/api/ngt

Authentication

All requests require a Bearer API key in the Authorization header. Generate keys from your dashboard.

# Every request needs this header Authorization: Bearer ngt_your_key_here

Keys start with ngt_. Treat them as secrets — do not expose in client-side code.

Errors

The API uses standard HTTP status codes. Error responses contain a JSON body with an error key.

Code	Meaning
401	Missing or invalid API key
403	Account has no active subscription
422	Request validation failed or model returned invalid output
429	Daily rate limit exceeded
503	Server Anthropic key not configured

Rate limits

Plan	Calls / day
Trial	20
NGT Studio Monthly	500
NGT Studio Yearly	2,000
NGT API	5,000

Limits reset at midnight UTC. Exceeded requests receive a 429 response with limit and reset fields.

POST /generate

Generate a complete document specification from a prompt. Uses Claude Sonnet. Returns a JSON spec you can render yourself or pass to /element for SVG output.

POST/api/ngt/generate

Request body

Field	Type	Required	Description
prompt	string	Yes	Plain-English description of the document. Max 2,000 chars.
format	string	No	Format preset key, e.g. `a4p`, `ig_sq`. Overrides auto-detect.

Example

curl https://nextgentext.online/api/ngt/generate \ -H "Authorization: Bearer ngt_..." \ -H "Content-Type: application/json" \ -d '{ "prompt": "A4 sustainability report for Birchwood Coffee 2024", "format": "a4p" }'

Response

{ "spec": { "documentType": "business_doc", "title": "Birchwood Coffee — Sustainability Report 2024", "format": { "preset": "a4p", "width": 1240, "height": 1754 }, "palette": { /* 8 colour roles */ }, "typography": { /* 6 type roles */ }, "layout": { /* margins and gaps */ }, "sections": [ /* array of section objects */ ] }, "model": "NGT-1", "engine": "ngt-sonnet" }

POST /edit

Apply iterative changes to an existing spec. Pass the current spec and a plain-English instruction. Returns an array of mutation commands you apply to the spec on your side.

POST/api/ngt/edit

Field	Type	Required	Description
spec	object	Yes	Current document spec (from `/generate` or your own).
instruction	string	Yes	Change instruction. Max 1,000 chars.

# Example instruction "instruction": "Make the accent colour darker and switch body font to Lora" # Response — array of mutation commands { "mutations": [ { "action": "set_palette", "key": "accent", "value": "#8b3a0f" }, { "action": "set_typography", "role": "body", "prop": "family", "value": "Lora" } ] }

POST /element

Generate a raw SVG fragment for a single section within exact pixel bounds. Uses Claude Haiku. This is the primitive that powers AI Elements mode in NGT Studio.

POST/api/ngt/element

Field	Required	Description
section	Yes	Section object (type + content).
bounds	Yes	`{"w": 1072, "h": 200}` — pixel dimensions.
palette	Yes	8-key colour palette object.
typography	Yes	Typography roles object.
context	No	One-line summary of other sections for layout context.
instruction	No	Optional variation instruction.

Response

{ "svg_fragment": "<rect width=\"1072\" height=\"200\" .../>\n<text ...", "bounds": { "w": 1072, "h": 200 }, "model": "NGT-1-mini" }

Wrap the fragment in a <g transform="translate(x,y)"> with a clipPath to assemble multiple elements into a full document SVG.

POST /validate

Validate a spec for common layout problems. Returns warnings without making any AI calls — instant, no tokens consumed.

POST/api/ngt/validate

{ "warnings": [ { "severity": "error", "message": "display font is 6px — below 8px minimum." }, { "severity": "warning", "message": "Section 3 table row 1: cell count ≠ header count." } ], "valid": false }

Spec schema

The document spec is the central data structure. Generate it with /generate, modify it with mutation commands from /edit, and render sections with /element.

{ "documentType": "business_doc", // infographic | social_post | poster | research_doc | ... "title": "Document Title", "format": { "preset": "a4p", // see /formats for all keys "width": 1240, "height": 1754, "dpi": 150 }, "palette": { "background": "#fff", "surface": "#f4f4f4", "surfaceAlt": "#e8e8e8", "accent": "#c8633a", "accentLight": "#fde8de", "text": "#1a1a18", "textMuted": "#6f6f6f", "border": "#e0d8cc" }, "typography": { "display": { "family": "Playfair Display", "size": 72, "weight": 700, "lineHeight": 1.1 }, "heading": { "family": "Playfair Display", "size": 36, "weight": 600, "lineHeight": 1.2 }, "subheading": { "family": "Inter", "size": 22, "weight": 400, "lineHeight": 1.3 }, "body": { "family": "Inter", "size": 16, "weight": 400, "lineHeight": 1.6 }, "caption": { "family": "Inter", "size": 12, "weight": 400, "lineHeight": 1.4 }, "label": { "family": "Inter", "size": 11, "weight": 600, "lineHeight": 1.2 } }, "layout": { "marginTop": 64, "marginRight": 64, "marginBottom": 64, "marginLeft": 64, "columnGap": 32, "sectionGap": 40 }, "sections": [ /* array of section objects */ ] }

Section types

Type	Key fields
hero	heading, subheading, align (left\|center)
heading	content, level (1\|2\|3)
body	content, columns (1\|2)
feature	icon (emoji), heading, body
stat_row	items: [{value, label}]
quote	content, attribution
list	items: [string]
columns	items: [{heading, body}]
image_block	imageId, caption, aspectRatio, altText
callout	label, content, labelColor
timeline	items: [{date, heading, body}]
table	headers: [], rows: [[]]
divider	—
caption	content
footer	content

Any section can include "bg": "#hex" for a full-bleed background colour behind that section.

Common format presets

Key	Name	Dimensions
a4p	A4 Portrait	1240 × 1754
a4l	A4 Landscape	1754 × 1240
letp	US Letter Portrait	1275 × 1650
pres169	Presentation 16:9	1920 × 1080
ig_sq	Instagram Post	1080 × 1080
ig_st	Instagram Story	1080 × 1920
li_p	LinkedIn Post	1200 × 628
tw_p	X (Twitter) Post	1200 × 675
bcard	Business Card	1050 × 600

50+ formats available. See full list in NGT Studio format selector.