Gemini 3.1 Pro Preview Custom Tools vs Gemini Robotics-ER 1.6 Preview
Gemini 3.1 Pro Preview Custom Tools (2026) and Gemini Robotics-ER 1.6 Preview (2026) are frontier reasoning models from Google DeepMind. Gemini 3.1 Pro Preview Custom Tools ships a 1m-token context window, while Gemini Robotics-ER 1.6 Preview ships a 128k-token context window. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Gemini 3.1 Pro Preview Custom Tools fits 8x more tokens; pick it for long-context work and Gemini Robotics-ER 1.6 Preview for tighter calls.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview Custom Tools | Gemini Robotics-ER 1.6 Preview |
|---|---|---|
| Best for | multimodal apps and long-context analysis | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | RAG, Long context, and Vision | RAG, Agents, and Long context |
| Context window | 1m | 128k |
| Cheapest output | $12/1M tokens | - |
| Provider routes | 1 tracked | 0 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Gemini 3.1 Pro Preview Custom Tools has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3.1 Pro Preview Custom Tools has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Gemini 3.1 Pro Preview Custom Tools for RAG, Long context, and Vision.
- Gemini Robotics-ER 1.6 Preview uniquely exposes Reasoning, Function calling, and Tool use in local model data.
- Local decision data tags Gemini Robotics-ER 1.6 Preview for RAG, Agents, and Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Gemini 3.1 Pro Preview Custom Tools
$4,600
Cheapest tracked route/tier: OpenRouter
Gemini Robotics-ER 1.6 Preview
Unavailable
No complete token price in local provider data
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 3.1 Pro Preview Custom Tools and Gemini Robotics-ER 1.6 Preview; plan for SDK, billing, or endpoint changes.
- Gemini Robotics-ER 1.6 Preview adds Reasoning, Function calling, and Tool use in local capability data.
- No overlapping tracked provider route is sourced for Gemini Robotics-ER 1.6 Preview and Gemini 3.1 Pro Preview Custom Tools; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Reasoning, Function calling, and Tool use before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-01-01 | 2026-04-14 |
| Context window | 1m | 128k |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use with conditions | Commercial use with conditions |
| Knowledge cutoff | 2025-01 | - |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview Custom Tools | Gemini Robotics-ER 1.6 Preview |
|---|---|---|
| Input price | $2/1M tokens | - |
| Output price | $12/1M tokens | - |
| Providers | - |
Capabilities
| Capability | Gemini 3.1 Pro Preview Custom Tools | Gemini Robotics-ER 1.6 Preview |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | Yes |
| Function calling | No | Yes |
| Tool use | No | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Gemini Robotics-ER 1.6 Preview, function calling: Gemini Robotics-ER 1.6 Preview, and tool use: Gemini Robotics-ER 1.6 Preview. Both models share vision, multimodal input, and structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
Pricing coverage is uneven: Gemini 3.1 Pro Preview Custom Tools has $2/1M input tokens and Gemini Robotics-ER 1.6 Preview has no token price sourced yet. Provider availability is 1 tracked routes versus 0. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose Gemini 3.1 Pro Preview Custom Tools when long-context analysis, larger context windows, and broader provider choice are central to the workload. Choose Gemini Robotics-ER 1.6 Preview when reasoning depth are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions.
FAQ
Which has a larger context window, Gemini 3.1 Pro Preview Custom Tools or Gemini Robotics-ER 1.6 Preview?
Gemini 3.1 Pro Preview Custom Tools supports 1m tokens, while Gemini Robotics-ER 1.6 Preview supports 128k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Is Gemini 3.1 Pro Preview Custom Tools or Gemini Robotics-ER 1.6 Preview open source?
Gemini 3.1 Pro Preview Custom Tools is listed under Proprietary. Gemini Robotics-ER 1.6 Preview is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Gemini 3.1 Pro Preview Custom Tools or Gemini Robotics-ER 1.6 Preview?
Both Gemini 3.1 Pro Preview Custom Tools and Gemini Robotics-ER 1.6 Preview expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, Gemini 3.1 Pro Preview Custom Tools or Gemini Robotics-ER 1.6 Preview?
Both Gemini 3.1 Pro Preview Custom Tools and Gemini Robotics-ER 1.6 Preview expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for reasoning mode, Gemini 3.1 Pro Preview Custom Tools or Gemini Robotics-ER 1.6 Preview?
Gemini Robotics-ER 1.6 Preview has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Gemini 3.1 Pro Preview Custom Tools and Gemini Robotics-ER 1.6 Preview?
Gemini 3.1 Pro Preview Custom Tools is available on OpenRouter. Gemini Robotics-ER 1.6 Preview is available on the tracked providers still being sourced. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-04. Data sourced from public model cards and provider documentation.