ArcFlow

02 Attach tools to agents

Before you start

Complete 01 Define a tool. You should know how to construct a Tool with name, description, input_schema, and execute.

Concept

Tools attach to agents, not directly to workflows. Pass a tuple of Tool instances to the agent constructor:

python
Agent(..., tools=(tool_a, tool_b))

The workflow still registers agents as steps (or graph nodes). When that step runs, the agent carries its tool list into the runtime.

Rules enforced at construction time:

RuleError if violated
Each entry must be a Tool instanceType validation in binding layer
Tool names must be unique within one agentWorkflowConfigurationError on duplicate name
At least zero tools is validAgents without tools behave like plain prompt steps

Multiple agents in one workflow can each carry different tool sets. A researcher might have no tools while a worker agent exposes several.

The stub provider may not exercise every tool call path the way a live model does. Tool attachment validation still runs, and integration tests confirm the wiring end to end.

Example

Two tools on one agent in a single-step workflow:

Save as attach_tools.py:

python
from arcflow import Agent, Tool, Workflow


def add_execute(payload: dict) -> str:
 a = float(payload.get("a", 0))
 b = float(payload.get("b", 0))
 return str(a + b)


def greet_execute(payload: dict) -> str:
 name = str(payload.get("name", "world"))
 return f"Hello, {name}!"


add_numbers = Tool(
 name="add_numbers",
 description="Add two numbers.",
 input_schema={
 "type": "object",
 "properties": {
 "a": {"type": "number"},
 "b": {"type": "number"},
 },
 "required": ["a", "b"],
 },
 execute=add_execute,
)

greet = Tool(
 name="greet",
 description="Greet someone by name.",
 input_schema={
 "type": "object",
 "properties": {"name": {"type": "string"}},
 "required": ["name"],
 },
 execute=greet_execute,
)

agent = Agent(
 name="assistant",
 role="Assistant",
 instructions="Help the user using available tools.",
 tools=(add_numbers, greet),
)

workflow = Workflow("attach-tools-demo")
workflow.step(agent)

result = workflow.run("Demonstrate tool wiring")
print(result.output)
print(f"status={result.status}")

Run:

bash
python attach_tools.py

Verify

CheckExpected
Script completesNo configuration error
Duplicate tool namesSecond tool with same name on one agent raises WorkflowConfigurationError

Duplicate name check:

python
from arcflow import Agent, Tool
from arcflow.exceptions import WorkflowConfigurationError

def stub_execute(_: dict) -> str:
 return "ok"

t1 = Tool("dup", "first", {"type": "object"}, stub_execute)
t2 = Tool("dup", "second", {"type": "object"}, stub_execute)

try:
 Agent(name="a", role="A", instructions="Run.", tools=(t1, t2))
except WorkflowConfigurationError as err:
 print(err)

Next

03 Tool loop and max iterations bounds how many tool rounds an agent may take in one step.

Previous

Define a tool

Next

Tool loop and max iterations