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ChatGPT: complete guide to API access and developer tools

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OpenAI has significantly expanded the ChatGPT API and its developer toolset, enabling creators, businesses, and enterprises to build powerful applications, agents, and data pipelines. As of August-September 2025, the API supports advanced endpoints, multimodal features, strict JSON outputs, and robust SDKs designed to integrate ChatGPT models into products and internal systems efficiently. This guide provides an updated and accurate breakdown of the available models, pricing, limits, and developer tools.



OpenAI’s API offers multiple endpoints for different use cases.

The ChatGPT API now supports multiple specialized endpoints, allowing developers to handle conversational logic, tool orchestration, file attachments, embeddings, and speech in a unified environment.

Endpoint

Purpose

Default models

Context window

/v1/chat/completions

Multi-turn conversations with memory

GPT-5, GPT-4.1, GPT-4o, GPT-3.5

Up to 128,000 tokens (Enterprise)

/v1/responses (beta)

Unified output orchestration with tools and files

GPT-5, GPT-4.1, GPT-4o, GPT-4o-mini

Up to 128,000 tokens

/v1/assistants

Manages multi-turn agentic workflows

GPT-4o-mini default

64,000 tokens

/v1/audio

Speech-to-text (Whisper v3) and TTS streaming

Dedicated models

N/A

/v1/images/generations

Image generation via DALL·E 3 and 3.5

DALL·E family

Up to 4 MP

/v1/embeddings

Vector embeddings for retrieval and RAG pipelines

text-embedding-4

8,000 tokens

Key update: The Responses API (currently in open beta) consolidates multi-modal features into a single endpoint, supporting structured tool calls, file returns, and streaming partial JSON.



Updated pricing for ChatGPT API models.

As of August/September 2025, OpenAI uses per-1M tokens pricing instead of per-1k for high-volume billing clarity.

Model

Input (per 1M tokens)

Output (per 1M tokens)

Fine-tune input

Fine-tune output

GPT-5

$1.25

$10.00

$6.00

$24.00

GPT-4.1

$8.00

$24.00

$3.00

$12.00

GPT-4o-mini

$4.00

$12.00

$0.80

$3.20

GPT-3.5-turbo

$0.50

$1.50

$0.12

$0.60

Recent change: On 27 Aug 2025, GPT-4.1’s prices increased to reflect model upgrades, affecting both API and Playground billing.



API usage limits and rate tiers.

API request capacity depends on the plan level, with higher tiers unlocking more throughput and larger context windows.

Plan

Max QPS

Token throughput (TPM)

Context window

Notes

Individual API key

3 QPS

10,000 TPM

16k–32k

For hobby projects and light apps

Plus / Team

10 QPS

40,000 TPM

Up to 64k

Ideal for advanced prototypes

Enterprise

50 QPS

500,000 TPM

Up to 128k

SLA-backed scaling and compliance

Developers working with higher-volume workloads can request custom throughput expansions and prioritized compute slots via Enterprise contracts.


Developer plans and add-ons.

Plan

Price / month

API benefits

Best for

ChatGPT Plus

$20

Doubled token throughput and 64k context in Playground

Individual developers

ChatGPT Team

$25 per seat

Shared billing, pooled usage quotas, and SSO integration

Small teams & startups

ChatGPT Enterprise

Custom pricing

128k context, SOC 2 compliance, zero data retention, and dedicated scaling

Enterprises

ChatGPT Go (India launch)

₹399

Adds 30k TPM, ADA access, and larger file uploads

Emerging markets

These plans unlock higher capacity for developers who require faster requests, larger data handling, and premium features like Advanced Data Analysis (ADA).


Official SDKs and developer tools.

OpenAI maintains a growing ecosystem of SDKs and CLI utilities designed to streamline API usage.


1. SDKs (Python & JavaScript, v2.3)

  • Unified API support for chat, responses, and assistants.

  • Built-in retry logic and rate-limit back-off handling.

  • Strict JSON schema enforcement for reliable outputs.


2. OpenAI CLI

# Deploy updated tool definitions
openai tools sync

# Execute a single Responses API call
openai responses create

# Upload files for ADA or Assistants API
openai files upload

3. Gradients Workspace

  • A cloud IDE designed for rapid prototyping.

  • Pre-wired GPT-4o kernel, integrated debugging, and 1 GB ephemeral storage.


Structured outputs and function-calling.

Strict JSON support ensures ChatGPT reliably returns predictable outputs—essential for applications requiring validated formats.

{
  "name": "create_event",
  "parameters": {
    "type": "object",
    "properties": {
      "title": {"type": "string"},
      "start": {"type": "string", "format": "date-time"},
      "duration_min": {"type": "integer"}
    },
    "required": ["title", "start", "duration_min"]
  }
}

By setting tool_choice and enabling tool_definition.strict=true, developers enforce guaranteed schema-perfect responses across models.


Advanced Data Analysis (ADA) capabilities via API.

Gemini now supports ADA-like workloads in the API, but OpenAI’s Advanced Data Analysis remains one of the most mature options:

  • Supported formats: CSV, XLSX, JSON, Parquet, base64 images, audio.

  • Limits:

    • Up to 10 files per request, 512 MB total size.

    • Spreadsheets limited to 50 MB each.

  • Execution: Sandbox runtime of 60 seconds for Plus/Team and 90 seconds for Enterprise.

  • Outputs: Generates processed datasets, plots, and downloadable files.


Migrating to the new Responses API.

The Responses API simplifies workflows by consolidating what previously required multiple endpoints.

Before

Now with Responses API

Separate /chat + /files requests

Single POST request with attachments[]

Polling threads manually

Streaming via SSE with partial JSON chunks

External tool orchestration

Native tools[] array with built-in retries and parallel function calls

Although the Responses API is still in beta, it is set to replace /v1/chat/completions in late 2026. Developers are encouraged to migrate gradually for better tooling and binary support.



Best practices for efficient usage.

  1. Stream responses wherever possible to reduce token costs and latency.

  2. Cache prompts for shared tasks—static instructions shouldn’t be resent each call.

  3. Use batch moderation endpoints to reduce costs when scanning multiple texts.

  4. Keep file uploads efficient by reusing stored IDs across sessions.

  5. Use pinned model IDs only when consistency matters; otherwise rely on gpt-4o-latest.


OpenAI’s developer ecosystem has evolved into a multi-layered API platform supporting advanced tools, custom integrations, streaming outputs, and enterprise-ready scaling. With updated pricing, unified endpoints, strict JSON outputs, and high-capacity developer plans, ChatGPT now powers solutions ranging from simple chatbots to mission-critical automation pipelines.


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