GPT-6.1 Terra - AnyFast

GPT-6.1 Terra is OpenAI’s fast, efficient model for visual reasoning, precise computer use, and clear writing. Use the model ID gpt-6.1-terra with the OpenAI-compatible Responses API at POST /v1/responses or Chat Completions at POST /v1/chat/completions.

Prefer the Responses API for function calling with reasoning, Structured Outputs, and prompt caching. AnyFast accepted basic Chat Completions text requests, but a Chat Completions function call at reasoning_effort: "low" returned 404 DeploymentNotFound.

Model specifications

Property	Value
Model ID	`gpt-6.1-terra`
Recommended API	Responses API
Input	Text and image
Output	Text
Context window (official specification)	1,050,000 tokens
Maximum output	128,000 tokens
Knowledge cutoff	June 1, 2026
Reasoning effort	`none`, `low`, `medium`, `high`, `xhigh`, `max`
Default reasoning effort	`medium`
Fine-tuning	Not supported

When to use GPT-6.1 Terra

Match product photos to catalog entries or interpret technical drawings.
Work with application screens in a defined computer-use workflow.
Draft and revise concise, natural text.
Handle scoped code fixes with clear acceptance criteria.
Analyze text and image inputs together.
Produce JSON that follows a strict schema.

Quick start

Responses API
Chat Completions

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6.1-terra",
    "input": "Summarize the key differences between these two product descriptions.",
    "reasoning": { "effort": "medium" },
    "max_output_tokens": 1024
  }'

cURL

curl https://www.anyfast.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6.1-terra",
    "messages": [
      { "role": "user", "content": "Summarize this product description." }
    ],
    "reasoning_effort": "medium",
    "max_completion_tokens": 1024
  }'

Tool calling

Use the Responses API when the model needs to reason and call tools:

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6.1-terra",
    "input": "Call get_weather for Paris.",
    "reasoning": { "effort": "medium" },
    "tools": [{
      "type": "function",
      "name": "get_weather",
      "description": "Get the weather for a city.",
      "parameters": {
        "type": "object",
        "properties": {
          "city": { "type": "string" }
        },
        "required": ["city"],
        "additionalProperties": false
      },
      "strict": true
    }],
    "tool_choice": "required"
  }'

A tested AnyFast Responses request returned a function_call item with name, arguments, and call_id. A Chat Completions function call at reasoning_effort: "low" returned 404 DeploymentNotFound; use Responses for tools.

Reasoning and sampling rules

Effort	Typical use
`none`	Simple tasks that do not need reasoning
`low`	Routine tasks with light reasoning
`medium`	General visual analysis and writing; the default
`high`	More difficult multi-step tasks
`xhigh`	Demanding visual or computer-use workflows
`max`	Maximum reasoning depth

AnyFast accepted all six reasoning efforts through Responses. At medium effort, temperature: 0.5 returned HTTP 400 with error.param: "temperature". When reasoning effort is not none, omit temperature, top_p, and top_logprobs. For Chat Completions, also omit logprobs; for Responses, do not request message.output_text.logprobs in include.

Core parameters

Parameter	API	Description
`model`	Both	Must be `gpt-6.1-terra`
`input`	Responses	Text or ordered input items, including images
`messages`	Chat Completions	Ordered conversation messages
`reasoning.effort`	Responses	`none`, `low`, `medium`, `high`, `xhigh`, or `max`; all live-tested
`reasoning_effort`	Chat Completions	`medium` was live-tested for text requests
`max_output_tokens`	Responses	Maximum visible output and reasoning tokens, up to 128,000
`max_completion_tokens`	Chat Completions	Maximum completion and reasoning tokens
`tools`	Responses	Top-level function tool definitions
`tool_choice`	Responses	`required` was live-tested with a function tool
`text.format`	Responses	Strict JSON Schema output succeeded in a live request
`prompt_cache_options.ttl`	Responses	`30m` was accepted; effective retention was not verified
`stream`	Both	Stream response events; both routes were live-tested

In tested AnyFast Responses JSON, text appeared in output[].content[].text on output_text blocks, and function calls appeared as output[] items. The raw JSON had no top-level output_text field. A strict JSON Schema request succeeded. A prompt_cache_options.ttl: "30m" request returned prompt_cache_retention: "24h"; the short prompt wrote no cache entry. Chat Completions returned model: "azure/gpt-6.1-terra" and omitted choices[].logprobs.

API Reference

View the GPT-6.1 Terra API reference.

​Model specifications

​When to use GPT-6.1 Terra

​Quick start

​Tool calling

​Reasoning and sampling rules

​Core parameters

API Reference

​Official references

Model specifications

When to use GPT-6.1 Terra

Quick start

Tool calling

Reasoning and sampling rules

Core parameters

Official references