Agents

Reviewed by Proof · Updated

Definition

An AI agent is a program that lets a model work toward a goal over several steps, choosing and using tools and checking the results as it goes.

Key takeaways

  • An agent runs a loop: the model decides the next step, the program runs it, and the result goes back to the model.
  • Tools are what let an agent act, such as reading files, running tests or searching. See Tool Calling.
  • Coding agents like Aider, Roo Code and OpenCode can use luv13 as their model.
  • Agents use many requests and a lot of tokens per task, because the growing history is sent each step.
  • Give agents clear limits: which tools they have, how many steps they can take, and what needs your approval.

The loop

  1. Goal. You give the task: "Fix the failing test in utils.py."
  2. Think and choose. The model reads the context and picks an action, often a tool call.
  3. Act. The program runs the tool and captures the output.
  4. Observe. The output is added to the conversation.
  5. Repeat until the model says it's done or a step limit is hit.

What makes agents work well

  • A model with solid tool calling. Some agents need it to work at all.
  • Good tools. Small, well-described tools with clear errors.
  • Feedback. Tests, linters and type checkers give the agent a way to check its own work.
  • Guardrails. Ask before risky actions, like deleting files, running shell commands or spending money.

Cost and context

Each step re-sends the conversation, so input tokens grow fast over a long task. On luv13 input and output cost the same per token (see Pricing), so the total token count is what drives cost. Watch usage and cap the number of steps. See Conversation History.

Example

This is one step of an agent loop: the model gets a tool and decides whether to call it.

curl https://api.luv13.ai/v1/chat/completions \
  -H "Authorization: Bearer $LUV13_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "luv13/glm-5.3-flash",
    "messages": [{"role": "user", "content": "How many files are in the src folder?"}],
    "tools": [{
      "type": "function",
      "function": {
        "name": "list_files",
        "description": "List files in a folder.",
        "parameters": {"type": "object", "properties": {"path": {"type": "string"}}, "required": ["path"]}
      }
    }]
  }'

Your program would run list_files, send the result back, and call the API again. See Tool Calling on luv13 for what luv13 supports.