GPT-5.5 Pro

OpenAIMCP Tool CallReasoning

openai/gpt-5.5-proClosed API

Highest-accuracy GPT-5.5 tier for slower, precision-heavy reasoning and coding

Benchmark Pricing$30.00 / 1M in$180.00 / 1M out

Context: 1,050,000 tokens•Max Output: 128,000 tokens•Knowledge: 2025-12-01•Released: 2026-04-23

TECHNICAL SPECIFICATIONS

Context Window1,050,0001.1M tokens

Max Output128,000128K tokens

LicenseProprietaryCloud API only

Input Modalities

TextVisionPDF

Function / Tool CallingSupported (MCP Ready)

Structured OutputsGuaranteed Schema

MODEL CONTEXT PROTOCOL (MCP) READINESS

✓ GPT-5.5 Pro natively supports OpenAI / Anthropic format tool calling and is fully compatible with MCP servers and agent loops.

MCP Context Window Recommendations

With a context capacity of 1,050,000 tokens, this model can handle extremely large MCP resource manifests, complete database schemas, and multiple active server tool definitions simultaneously without degradation.

STANDARDIZED BENCHMARKS & EVALS

BrowseCompaccuracy

90.1

Humanity's Last Examaccuracy

43.1

Humanity's Last Examaccuracy

57.2

FrontierMathaccuracy

52.4

FrontierMathaccuracy

39.6

GDPvalwins or ties

82.3

GeneBenchaccuracy

33.2

API CALL INVOCATION EXAMPLE

// Example: Calling GPT-5.5 Pro via OpenAI SDK
import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY,
});

const response = await client.chat.completions.create({
  model: "openai/gpt-5.5-pro",
  messages: [{ role: "user", content: "Hello! Can you inspect MCP tools?" }],
});

console.log(response.choices[0].message.content);