Foundation Model
A large AI model pre-trained on broad data that serves as the base for many downstream applications. Foundation models (GPT-4, Claude, Gemini, Llama) are 'foundational' because they're not built for a single task—they're adapted through prompting, fine-tuning, or RAG to power diverse agents. Choosing the right foundation model for your agent affects cost, speed, accuracy, and capabilities.
Written by Max Zeshut
Founder at Agentmelt · Last updated Sep 9, 2026
Example
A company builds three different agents on the same foundation model (Claude): a support agent for ticket deflection, a sales agent for outbound emails, and a data agent for SQL generation. Each uses different prompts and tools, but shares the same underlying reasoning capabilities.
Frequently asked questions
- How do I choose a foundation model for my agent?
- Consider: task complexity (frontier models for reasoning-heavy tasks, smaller models for classification), latency requirements (smaller models are faster), cost (prices range 10x between model tiers), data privacy (some require self-hosting), and specific capabilities (coding, vision, multilingual). Most teams start with a frontier model to validate, then optimize to smaller models where quality allows.