flatagents 0.1.5

A lightweight framework for building LLM-powered agents with pluggable backends.

FlatAgents Python SDK

Status: Prototype

Python SDK for FlatAgents—a format for defining AI agents. Write your agent config once, run it anywhere. See the spec.

In Progress

• Unify input/output adapters for agent chaining
• Simplify output adapters
• Add workflows (flatworkflows)
• TypeScript SDK

Why FlatAgents?

Agent configs are portable. Write your agent YAML once, run it with any SDK that implements the spec. Share agents across teams, languages, and frameworks. Want an SDK for your language? Build one—the spec is simple.

Agent Definition

Define agents in YAML or JSON. Both formats are first-class.

agent.yml

spec: flatagent
spec_version: "0.6.0"

data:
  name: summarizer
  model:
    provider: openai
    name: gpt-4o-mini
  system: You summarize text concisely.
  user: "Summarize this: {{ input.text }}"
  output:
    summary:
      type: str
      description: A concise summary

agent.json

{
  "spec": "flatagent",
  "spec_version": "0.6.0",
  "data": {
    "name": "summarizer",
    "model": {
      "provider": "openai",
      "name": "gpt-4o-mini"
    },
    "system": "You summarize text concisely.",
    "user": "Summarize this: {{ input.text }}",
    "output": {
      "summary": {
        "type": "str",
        "description": "A concise summary"
      }
    }
  }
}

from flatagents import FlatAgent

agent = FlatAgent(config_file="agent.yml")  # or agent.json
result = await agent.execute(input={"text": "Long article here..."})
print(result["summary"])

Quick Start

pip install flatagents[litellm]

writer.yaml

spec: flatagent
spec_version: "0.6.0"

data:
  name: writer
  model:
    provider: openai
    name: gpt-4o-mini
  system: You write short, punchy marketing copy.
  user: |
    Product: {{ input.product }}
    {% if input.feedback %}Previous attempt: {{ input.tagline }}
    Feedback: {{ input.feedback }}
    Write an improved tagline.{% else %}Write a tagline.{% endif %}
  output:
    tagline:
      type: str
      description: The tagline

critic.yaml

spec: flatagent
spec_version: "0.6.0"

data:
  name: critic
  model:
    provider: openai
    name: gpt-4o-mini
  system: You critique marketing copy. Be constructive but direct.
  user: |
    Product: {{ input.product }}
    Tagline: {{ input.tagline }}
  output:
    feedback:
      type: str
      description: Constructive feedback
    score:
      type: int
      description: Score from 1-10

run.py

import asyncio
from flatagents import FlatAgent

async def main():
    writer = FlatAgent(config_file="writer.yaml")
    critic = FlatAgent(config_file="critic.yaml")

    product = "a CLI tool for AI agents"
    draft = await writer.execute(input={"product": product})

    for round in range(4):
        review = await critic.execute(input={"product": product, **draft})
        print(f"Round {round + 1}: \"{draft['tagline']}\" - {review['score']}/10")

        if review["score"] >= 8:
            break
        draft = await writer.execute(input={"product": product, **review, **draft})

    print(f"Final: {draft['tagline']}")

asyncio.run(main())

export OPENAI_API_KEY="your-key"
python run.py

Usage

From Dictionary

from flatagents import FlatAgent

config = {
    "spec": "flatagent",
    "spec_version": "0.6.0",
    "data": {
        "name": "calculator",
        "model": {"provider": "openai", "name": "gpt-4"},
        "system": "You are a calculator.",
        "user": "Calculate: {{ input.expression }}",
        "output": {
            "result": {"type": "float", "description": "The calculated result"}
        }
    }
}

agent = FlatAgent(config_dict=config)
result = await agent.execute(input={"expression": "2 + 2"})

Custom Agent (Subclass FlatAgent)

from flatagents import FlatAgent

class MyAgent(FlatAgent):
    def create_initial_state(self):
        return {"count": 0}

    def generate_step_prompt(self, state):
        return f"Count is {state['count']}. What's next?"

    def update_state(self, state, result):
        return {**state, "count": int(result)}

    def is_solved(self, state):
        return state["count"] >= 10

agent = MyAgent(config_file="config.yaml")
trace = await agent.execute()

LLM Backends

Two backends available:

from flatagents import LiteLLMBackend, AISuiteBackend

# LiteLLM - model format: provider/model
backend = LiteLLMBackend(model="openai/gpt-4o", temperature=0.7)

# AISuite - model format: provider:model
backend = AISuiteBackend(model="openai:gpt-4o", temperature=0.7)

Custom Backend

Implement the LLMBackend protocol:

class MyBackend:
    total_cost: float = 0.0
    total_api_calls: int = 0

    async def call(self, messages: list, **kwargs) -> str:
        self.total_api_calls += 1
        return "response"

agent = MyAgent(backend=MyBackend())

Examples

More examples are available in the examples/ directory:

• helloworld - Minimal getting started example
• writer_critic - Iterative refinement with two agents
• mdap - Multi-step reasoning with calibrated confidence
• gepa_self_optimizer - Self-optimizing prompt evolution

Known Issues

aisuite drops tools from API calls

When using the aisuite backend with tool calling (MCP), tools are silently dropped from the API request unless max_turns is set. This is a bug in aisuite's client.chat.completions.create() which pops the tools kwarg.

Workaround: The SDK includes a direct provider call for Cerebras that bypasses aisuite's client. See _call_aisuite_cerebras_direct() in flatagent.py. Other providers may need similar workarounds until aisuite fixes this upstream.

Symptoms: Model outputs tool call JSON in text content instead of using actual tool calling mechanism. Agent completes immediately with "no tool calls" when tools should have been invoked.

License

MIT License - see LICENSE for details.