Current as of March 2026. GPT-5.1 sits at an interesting price point: $1.25/M input is reasonable, $10/M output is where you have to think carefully. The 128K output ceiling is the key differentiator — for tasks where you need a long, complex response, most other models cap out well before this.
Specs
| Provider | OpenAI |
| Input cost | $1.25 / M tokens |
| Output cost | $10 / M tokens |
| Context window | 272K tokens |
| Max output | 128K tokens |
| Parameters | N/A |
| Features | function_calling, vision, reasoning, web_search |
What it’s good at
128K Output
Few models generate this much text in a single pass. Multi-file code generation, large refactors, long documentation — these are where the output ceiling matters.
Function Calling
OpenAI’s tool use is still the most predictable on the market for complex schemas. It rarely hallucinates arguments.
Where it falls short
Output Cost
$10/M is expensive if you’re actually using the full 128K output regularly. Model the cost before committing.
Middle-of-Context Retrieval
I’ve noticed accuracy drops for details buried in the middle of the 272K window. If you have important information, put it at the start or end.
Best use cases with OpenClaw
- Long-form Code Generation — Writing full multi-file modules without mid-generation cutoffs.
- Research Agents — Web search plus reasoning makes it solid for OpenClaw agents that need to browse, verify, and synthesize.
Not ideal for
- Low-latency Chat — Slower than the mini variants, and the pricing is overkill for simple interactions.
- High-volume Summarization — GPT-4o-mini or Claude Haiku will do basic text processing for a fraction of the cost.
Run it through Haimaker
Skip juggling API keys. One Haimaker key gives you access to every model on the platform. Tell OpenClaw:
Add Haimaker as a custom provider to my OpenClaw config. Use these details:
- Provider name: haimaker
- Base URL: https://api.haimaker.ai/v1
- API key: [PASTE YOUR HAIMAKER API KEY HERE]
- API type: openai-completions
Add the auto-router model:
- haimaker/auto (reasoning: false, context: 128000, max tokens: 32000)
Create an alias "auto" for easy switching. Apply the config when done.
Or skip model selection entirely — Haimaker’s auto-router picks the best model for each task so you don’t have to.
OpenClaw setup
OpenClaw has native support for OpenAI, so you just need to export your OPENAI_API_KEY. No custom provider configuration or base URL overrides are required.
export OPENAI_API_KEY="your-key-here"
That’s it. OpenClaw picks up OpenAI models automatically.
How it compares
- vs Claude 3.5 Sonnet — Sonnet writes better code in my experience, but its 8K output cap is a real constraint. GPT-5.1 wins when output length matters.
- vs Gemini 1.5 Pro — Gemini has a 2M context window, which is more than GPT-5.1’s 272K. But I find GPT-5.1 more consistent on complex reasoning.
Bottom line
Worth it when you need 128K of coherent output. For shorter tasks, the $10/M output rate doesn’t pencil out — use GPT-4o-mini instead.
For setup instructions, see our API key guide. For all available models, see the complete models guide.