Best AI model API for apps and agents
Updated · What changed: First published with a three-tier routing recommendation.
By The AI Loadout editors · How we pick
For most apps, start with a mid-priced model such as Claude Sonnet 5.5 or GPT-6.1 Sol at $2 in and $10 out per million tokens, then route easy calls to a cheap model like GPT-6 Luna or Claude Haiku 5.5 at $0.10 in and $0.50 out. Reach for GPT-6 Astra or Claude Fable 5.1 ($10 in, $50 out) only for the hardest reasoning. Open-weight APIs such as DeepSeek V4 Pro, GLM-5.3 and Qwen3.8 Max cost far less for strong coding.
| Slot | Pick |
|---|---|
| Tool | Agent Project Manager pack |
| Model | Claude Sonnet 5.5 |
| Skill | Prompt caching |
| Persona | The API Router |
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The loadout (why each pick)
Tool: Agent Project Manager pack
Scores each task and routes it to the cheapest model tier that can handle it, so you do not pay frontier prices for easy calls. The tier file lists the models on this page with editable prices.
Model: Claude Sonnet 5.5
A strong default at $2 in and $10 out per million tokens with a 1M-token context window, per Anthropic docs.
Agent skills
- Prompt caching: Every provider here discounts repeated prompt prefixes, often by 90%. Put long system prompts and documents first so they cache.
Bot persona: The API Router
A short system prompt keeps cheap models on task.
Comparison table
| Option | Best for | Model(s) | Price | Free plan | Last checked |
|---|---|---|---|---|---|
| GPT-6 Astra | Hardest reasoning and computer use | OpenAI, 1.05M context | $10 in / $50 out | No | |
| Claude Fable 5.1 | Long-horizon agents | Anthropic, 1M context | $10 in / $50 out | No | |
| GPT-6 Luna | Cheap extraction and classification | OpenAI, 1.05M context | $0.10 in / $0.50 out | No | |
| Gemini 3.8 Flash | Fast multimodal calls, free tier | Google, 1M context | $0.75 in / $3.75 out (intro) | Yes | |
| Grok 4.7 | Low output price with web and X search | xAI, 500K context | $2 in / $6 out | No | |
| Muse Spark 1.3 | Agentic workflows with audio and video input | Meta, 1M context | $1.25 in / $4.25 out | No | |
| Mistral Large 4 | EU provider, open weights coming | Mistral, 1M context | $1.36 in / $4.18 out (half during launch sale) | No | |
| DeepSeek V4 Pro | Cheapest strong reasoning, off-peak | DeepSeek, 1M context | $1.32 in / $3.96 out peak, half off-peak | No | |
| Qwen3.8 Max | Engineering-scale coding and vision | Alibaba, 1M context | $2 in / $6 out | No | |
| Kimi K3 | Long-horizon coding, open weights | Moonshot, 1M context | $3 in / $15 out | No | |
| GLM-5.3 | Repository-scale coding agents | Z.ai, 1M context | $1.40 in / $4.40 out | No | |
| Amazon Nova Premier | Teams billing through AWS | Amazon Bedrock | $2.50 in / $12.50 out | No | |
| Cohere Command A+ | Enterprise RAG and translation, self-hostable | Cohere, 128K context | Free on Cohere API (rate limited) | Yes |
Prices come from the linked vendor or source page and can change. Check the vendor before you buy.
Copy this setup
Paste this persona into your tool's custom instructions or project instructions:
You are a precise assistant inside an app. Follow the output format exactly. If the input is missing information you need, return a short error explaining what is missing instead of guessing. Do not add commentary outside the requested format. No em dashes.- Write 20 real test prompts from your app before choosing.
- Run them on one cheap, one mid and one frontier model from the table.
- Use the cheapest model that passes for each task type, and cache long prompts.
- Re-check prices monthly; several of the prices below are launch or intro prices.
Alternatives by situation
- Tight budget: GPT-6 Luna or Claude Haiku 5.5 at $0.10 in and $0.50 out, or DeepSeek V4.1 Flash at $0.15 in off-peak.
- Hardest tasks: GPT-6 Astra or Claude Fable 5.1. Both cost $10 in and $50 out, so route only the hard calls there.
- Data residency: Mistral for an EU provider, Amazon Nova or models on Bedrock to stay inside AWS, or self-host an open-weight model such as Command A+ or GLM-5.3.
- Zero API cost: Run an open-weight model on your own hardware. See how to run AI locally.
What changed
- : Page launched with initial picks. Sources are listed at the bottom of the page.
FAQ
What is the cheapest good AI API?
As of Oct 15, 2026, GPT-6 Luna and Claude Haiku 5.5 both list at $0.10 per million input tokens and $0.50 per million output tokens. Cohere lists Command A+ as free on its API with rate limits.
Which AI API is the most capable?
GPT-6 Astra from OpenAI and Claude Fable 5.1 from Anthropic are each lab's top model, both at $10 in and $50 out per million tokens.
Are open-weight model APIs good enough?
For coding and agents, often yes. DeepSeek V4 Pro, GLM-5.3, Qwen3.8 Max and Kimi K3 are strong and cost less than most closed frontier models.
Why do prices on this page say intro or sale?
Google and Mistral launched models at temporary prices. Gemini 3.8 Flash doubles on Jan 1, 2027, and the Mistral Large 4 launch sale lasts two weeks from Oct 6, 2026.
Sources
- OpenAI API models
- Anthropic models overview
- Gemini API pricing
- xAI: Grok 4.7
- DeepSeek API pricing
- Amazon Bedrock pricing
- Cohere pricing
Disclosure: links marked "affiliate" may earn us a commission, and sponsored slots are always labeled. Neither affects our picks. Read our methodology.