Choose Google: Gemini 3.1 Pro Preview Custom Tools if…
- you need built-in web search — to answer from live web results; Meta: Muse Spark Open does not advertise it
Google: Gemini 3.1 Pro Preview Custom Tools vs Meta: Muse Spark Open
Neither wins outright: Google: Gemini 3.1 Pro Preview Custom Tools is the pick when you need built-in web search, Meta: Muse Spark Open when cost matters at scale.
Key numbers
| Spec | Google: Gemini 3.1 Pro Preview Custom Tools | Meta: Muse Spark Open |
|---|---|---|
| Provider | Meta | |
| Input price (per 1M tokens) | $2.00 | $1.25 |
| Output price (per 1M tokens) | $12.00 | $4.25 |
| Blended price (3:1 input/output) | $4.50 | $2.00 |
| Cheaper than … of all models we track | 12% | 25% |
| Context window | 1.0M tokens (~1,573 pages) | 1.0M tokens (~1,573 pages) |
| Larger context than … of all models | 81% | 81% |
| Max output per response | 66K tokens (~49,200 words) | 944K tokens (~707,800 words) |
| Input types | text, audio, image, video, file | text, image, video, file, audio |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-02-25 | 2026-10-15 |
What it costs for real workloads
Monthly cost at list price for five common workloads. Token counts per unit are stated so you can scale them to your own traffic. A workload that does not fit a model's context window is marked rather than priced.
| Workload (per month) | Google: Gemini 3.1 Pro Preview Custom Tools | Meta: Muse Spark Open | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $390 | $179 | Meta: Muse Spark Open saves $211 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $360 | $193 | Meta: Muse Spark Open saves $168 |
| Coding / tool-using agent 2,000 tasks — each a multi-step task with tool calls and file context (60,000 in / 6,000 out tokens) | $384 | $201 | Meta: Muse Spark Open saves $183 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $232 | $126 | Meta: Muse Spark Open saves $106 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $112 | $66.75 | Meta: Muse Spark Open saves $45.25 |
Capabilities side by side
| Capability | Google: Gemini 3.1 Pro Preview Custom Tools | Meta: Muse Spark Open | What it lets you do |
|---|---|---|---|
| Tool / function calling | ✓ Yes | ✓ Yes | call your APIs and run agent loops |
| Structured output (JSON schema) | ✓ Yes | ✓ Yes | return JSON that validates against your schema |
| Reasoning / thinking mode | ✓ Yes | ✓ Yes | spend extra tokens thinking before answering hard problems |
| Image input | ✓ Yes | ✓ Yes | read screenshots, charts and scanned pages |
| Audio input | ✓ Yes | ✓ Yes | take speech or audio directly |
| File / PDF input | ✓ Yes | ✓ Yes | accept documents without your own parsing step |
| Image output | — | — | generate images, not just text |
| Built-in web search | ✓ Yes | — | answer from live web results |
| Seed (reproducible sampling) | ✓ Yes | ✓ Yes | repeat a generation for tests and evals |
| Log-probabilities | — | ✓ Yes | read token confidence for classification and scoring |
From each model's published parameters and input/output types. “—” means not advertised, not proven absent.
Price history
- Google: Gemini 3.1 Pro Preview Custom Tools: price unchanged since we started tracking it on 2026-03-10.
- Meta: Muse Spark Open: price unchanged since we started tracking it on 2026-10-16.
Which should you choose?
Choose Meta: Muse Spark Open if…
- cost matters at scale — it is 56% cheaper on a typical 3:1 input/output mix ($179 vs $390 a month for 50,000 support chats)
- you need log-probabilities — to read token confidence for classification and scoring; Google: Gemini 3.1 Pro Preview Custom Tools does not advertise it
- you generate long outputs in one go — up to 944K tokens (about 707,800 words) per response
- you want the newer model — released 2026-10-15, 8 months after the other
Frequently asked questions
Is Google: Gemini 3.1 Pro Preview Custom Tools better than Meta: Muse Spark Open?
Neither wins outright: Google: Gemini 3.1 Pro Preview Custom Tools is the pick when you need built-in web search, Meta: Muse Spark Open when cost matters at scale. In short: Google: Gemini 3.1 Pro Preview Custom Tools when you need built-in web search; Meta: Muse Spark Open when cost matters at scale, you need log-probabilities, you generate long outputs in one go, you want the newer model.
Which is cheaper, Google: Gemini 3.1 Pro Preview Custom Tools or Meta: Muse Spark Open?
Meta: Muse Spark Open is cheaper: $2.00 vs $4.50 per 1M tokens at a typical 3:1 input/output mix, 56% less. For 50,000 support conversations a month that is $179 against $390.
How much do Google: Gemini 3.1 Pro Preview Custom Tools and Meta: Muse Spark Open cost per million tokens?
Google: Gemini 3.1 Pro Preview Custom Tools costs $2.00 per 1M input tokens and $12.00 per 1M output tokens; Meta: Muse Spark Open costs $1.25 input and $4.25 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, Google: Gemini 3.1 Pro Preview Custom Tools or Meta: Muse Spark Open?
Both take 1.0M tokens per request — roughly 1,573 pages of text.
Do Google: Gemini 3.1 Pro Preview Custom Tools and Meta: Muse Spark Open support function calling and JSON output?
Tool calling — Google: Gemini 3.1 Pro Preview Custom Tools: yes, Meta: Muse Spark Open: yes. JSON-schema structured output — Google: Gemini 3.1 Pro Preview Custom Tools: yes, Meta: Muse Spark Open: yes.
Can Google: Gemini 3.1 Pro Preview Custom Tools or Meta: Muse Spark Open read images?
Yes, both accept image input.
Is Google: Gemini 3.1 Pro Preview Custom Tools or Meta: Muse Spark Open free to use?
No free variant is listed for either; both are pay-per-token.
What is the maximum output length of Google: Gemini 3.1 Pro Preview Custom Tools and Meta: Muse Spark Open?
Google: Gemini 3.1 Pro Preview Custom Tools can write up to 66K tokens (about 49,200 words) per response; Meta: Muse Spark Open up to 944K (about 707,800 words).
When were Google: Gemini 3.1 Pro Preview Custom Tools and Meta: Muse Spark Open released?
Google: Gemini 3.1 Pro Preview Custom Tools was listed on 2026-02-25; Meta: Muse Spark Open on 2026-10-15.
About the two models
Google: Gemini 3.1 Pro Preview Custom Tools
Gemini 3.1 Pro Preview Custom Tools is a variant of Gemini 3.1 Pro that improves tool selection behavior by preventing overuse of a general bash tool when more efficient third-party...
Full Google: Gemini 3.1 Pro Preview Custom Tools specs →Meta: Muse Spark Open
Muse Spark Open is a coding-optimized open-weight model. Trained specifically for agentic coding workflows, it delivers higher first-attempt accuracy, reliable tool calling, and deep codebase understanding across the repos developers...
Full Meta: Muse Spark Open specs →