> ## Documentation Index > Fetch the complete documentation index at: https://docs.anyfast.ai/llms.txt > Use this file to discover all available pages before exploring further. # GPT-6.1 Sol > Use OpenAI GPT-6.1 Sol through AnyFast for complex coding, agentic workflows, reasoning, vision, and structured output. GPT-6.1 Sol is OpenAI's balanced model for complex coding, computer use, and professional work. Use the model ID `gpt-6.1-sol` 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 also accepted a Chat Completions function call at `reasoning_effort: "low"`; the Responses route follows OpenAI's tool guidance. ## Model specifications | Property | Value | | - | - | | Model ID | `gpt-6.1-sol` | | 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 | April 30, 2026 | | Reasoning effort | `low`, `medium`, `high`, `xhigh`, `max` | | Default reasoning effort | `medium` | | Fine-tuning | Not supported | ## When to use GPT-6.1 Sol * Complex software engineering and codebase-wide changes * Long-running agent workflows that use function calls * Multi-step planning, debugging, and technical analysis * Large-context document or repository analysis * Vision tasks that combine text and image input * Schema-constrained JSON output ## Quick start ```bash cURL theme={null} curl https://www.anyfast.ai/v1/responses \ -H "Authorization: Bearer YOUR_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "gpt-6.1-sol", "input": "Review this retry design, identify race conditions, and propose a safe implementation plan.", "reasoning": { "effort": "high", "summary": "auto" }, "max_output_tokens": 4096 }' ``` ```bash cURL theme={null} curl https://www.anyfast.ai/v1/chat/completions \ -H "Authorization: Bearer YOUR_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "gpt-6.1-sol", "messages": [ { "role": "user", "content": "Return a concise deployment checklist." } ], "reasoning_effort": "medium", "max_completion_tokens": 2048 }' ``` ## Tool calling Use the Responses API when the model needs to reason and call tools: ```bash cURL theme={null} curl https://www.anyfast.ai/v1/responses \ -H "Authorization: Bearer YOUR_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "gpt-6.1-sol", "input": "Check the deployment status for api-gateway.", "reasoning": { "effort": "high" }, "tools": [{ "type": "function", "name": "get_deployment_status", "description": "Return the current deployment status for a service.", "parameters": { "type": "object", "properties": { "service": { "type": "string" } }, "required": ["service"], "additionalProperties": false }, "strict": true }], "tool_choice": "auto" }' ``` AnyFast accepted Chat Completions function calling at `reasoning_effort: "low"`, returning `choices[].message.tool_calls` and `finish_reason: "tool_calls"`. OpenAI recommends the Responses API for tool calling. ## Reasoning and sampling rules | Effort | Typical use | | - | - | | `low` | Routine tasks with light reasoning | | `medium` | General coding and analysis; the default | | `high` | Complex multi-step work | | `xhigh` | Difficult professional and engineering tasks | | `max` | Maximum reasoning depth | For GPT-6.1 Sol, omit `temperature`, `top_p`, and `top_logprobs`. For Chat Completions, also omit `logprobs`; `reasoning_effort: "none"` returned `400` on AnyFast. For Responses, do not request `message.output_text.logprobs` in `include`. ## Core parameters | Parameter | API | Description | | - | - | - | | `model` | Both | Must be `gpt-6.1-sol` | | `input` | Responses | Text or ordered input items | | `messages` | Chat Completions | Ordered conversation messages | | `reasoning.effort` | Responses | `low`, `medium`, `high`, `xhigh`, or `max` | | `reasoning_effort` | Chat Completions | Same effort values as Responses | | `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` | Both | Responses uses top-level function fields; AnyFast Chat Completions accepts a nested `function` object. | | `text.format` | Responses | Text or strict JSON Schema output configuration | | `prompt_cache_options.ttl` | Responses | A `30m` request was accepted, but actual retention was not verified. | | `stream` | Both | Stream response events | In tested AnyFast Responses JSON, read text from `output[].content[].text` where the content block has `type: "output_text"`; function calls appear as `output[]` items with `type: "function_call"`. The raw response 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 did not write a cache entry, so effective retention remains unverified. Chat Completions returned `model: "azure/gpt-6.1-sol"` for the public request ID `gpt-6.1-sol`. View the GPT-6.1 Sol API reference. ## Official references * [GPT-6.1 Sol model page](https://developers.openai.com/api/docs/models/gpt-6.1-sol) * [Using GPT-6](https://developers.openai.com/api/docs/guides/latest-model)