Choosing a Model

​

Overview

Aster Agents supports bring-your-own-API-key across multiple providers. You connect your own API keys in Control Hub > Providers, then select a model when building each agent. This gives you full control over cost, performance, and provider choice.

​

Supported Providers

Add your API key in Control Hub > Providers to unlock that provider’s models across all your agents.

​

Recommended Models

These are the three models you should be choosing between for most agents:

​

Claude Sonnet 4.6 — Best All-Around

The default choice for most agents. Near-flagship intelligence at mid-tier pricing with the fastest output speed of any frontier model. Best for: General-purpose agents, CRM workflows, document analysis, data extraction, customer-facing agents, scheduled tasks, multi-tool orchestration. Why Sonnet over Opus? Sonnet 4.6 scores within 1-2% of Opus 4.6 on coding and agentic benchmarks (79.6% vs 80.8% on SWE-bench) while being significantly faster and 40% cheaper. For most agent tasks — querying databases, filling out forms, searching knowledge bases, writing emails — the difference is imperceptible.

---

​

Claude Opus 4.6 — Maximum Capability

The most capable model for tasks requiring deep reasoning, complex multi-step planning, or handling ambiguous instructions. Best for: Legal document analysis, financial modeling, research agents, complex multi-agent workflows, agents that need to handle edge cases gracefully, tasks where accuracy matters more than cost. When to choose Opus: When your agent regularly encounters situations that require judgment calls — interpreting vague requirements, handling conflicting information, or producing output where subtle errors have real consequences.

---

​

GPT-5.4 — Strong Alternative

OpenAI’s flagship. Competitive with Claude Opus on overall benchmarks, with slightly different strengths. Best for: Agents that need OpenAI’s built-in tools (web search, code interpreter, image generation), teams already invested in the OpenAI ecosystem, general-purpose agents where input cost sensitivity matters. OpenAI-exclusive tools: GPT-5.4 unlocks web_search, code_interpreter, and image_generation as provider tools — these aren’t available with other providers.

---

​

Budget-Friendly Options

For high-volume or cost-sensitive workloads: These models are excellent for multi-agent workflows where a cheaper model handles routine subtasks (classification, data formatting, simple lookups) while a flagship model handles the complex reasoning.

​

Choosing by Use Case

​

Cost Optimization Tips

1. Start with Sonnet 4.6 — it handles 90%+ of agent tasks well. Only upgrade to Opus if you see quality issues on specific tasks.
2. Use cheaper models for subagents — in multi-agent workflows, the orchestrator can run on Sonnet while worker agents run on Haiku or GPT-5.4 Mini.
3. Prompt caching saves money — both Anthropic (90% off cached input) and OpenAI (50% off cached input) automatically cache repeated context. Agents with large system prompts or knowledge base content benefit significantly.
4. Keep system prompts focused — longer prompts cost more on every message. A concise, well-structured prompt outperforms a verbose one and costs less.

​

Provider Tools

Some providers include built-in tools that extend your agent’s capabilities beyond Aster’s standard tool library: These tools appear automatically when you select a model from the corresponding provider. They can be enabled alongside Aster’s standard tools.