Agents & tools · Glossary term
What is Function Calling?
A provider or application interface through which a model emits a structured request naming a tool and its arguments. Application code validates the request, performs the operation, and can return the result for another model step.
“A model using tools.”
What is the common confusion about Function Calling?
The model requests a function call; your trusted code decides whether and how to execute it. Function calling alone is not a complete agent.
Learn Function Calling in the course
Start with
- Function Calling & Tool Use
LLMs cannot do anything. They generate text. That is the entire capability. They cannot check the weather, query a database, send an email, run code, or read a file.
Lessons that name Function Calling in a title or section
- Function Calling Deep Dive — OpenAI, Anthropic, Gemini
The three frontier providers converged on the same tool-call loop in 2024 and then diverged on everything else. OpenAI uses tools and toolcalls. Anthropic uses tooluse and toolresult blocks.
- Tool Use and Function Calling
Toolformer (Schick et al., 2023) started self-supervised tool annotation. Berkeley Function Calling Leaderboard V4 (Patil et al., 2025) sets the 2026 bar: 40% agentic, 30% multi-turn, 10% live, 10%…
- Structured Outputs: JSON, Schema Validation, Constrained Decoding
Your LLM returns a string. Your application needs JSON. That gap has crashed more production systems than any model hallucination.
Taught in Phase 11: LLM Engineering.
Also covered in Phase 13: Tools & Protocols and Phase 14: Agent Engineering.
Related terms
- Structured OutputModel output constrained or validated against a machine-readable schema so application code can consume fields without parsing free-form…
- Tool ContractThe complete agreement for a tool boundary: purpose, typed inputs, outputs, validation, permissions, side effects, errors, timeouts,…
- AgentA software system that lets a model select actions toward a goal, observe tool or environment results, and continue under an orchestration…
- MCP (Model Context Protocol)An open JSON-RPC protocol for a host to connect to servers that expose tools, resources, prompts, and extensions through defined request,…
- ReActAn agent pattern that interleaves task reasoning, a concrete action, and an observation returned by the environment before deciding the…
More terms in Agents & tools
- Agent
- Agent Harness
- Agent Memory
- Agent State
- Agent Skill
- Approval Gate
- Checkpoint
- Compensating Action
- Delegation
- Durable Execution
- Human-in-the-Loop (HITL)
- MCP (Model Context Protocol)
- Multi Round-Trip Request (MRTR)
- Orchestration
- Planning
- ReAct
- Sandbox
- Skill Bundle
- Skill Catalog
- Skill Discovery
- Skill Invocation
- Stateless MCP
- Structured Output
- Swarm
- Termination Condition
- Tool Contract
This entry comes from glossary/terms.md on GitHub. Browse all 250 glossary terms.