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Creating custom agent

This guide demonstrates how to create custom agents tailored for specific use cases. Using the planning agent as a concrete example, you'll learn how to design specialized agents with custom tool sets, system prompts, and configurations that optimize performance for particular workflows.

The example showcases a two-phase workflow where a custom planning agent (with read-only tools) analyzes tasks and creates structured plans, followed by an execution agent that implements those plans with full editing capabilities.

#!/usr/bin/env python3
"""
Planning Agent Workflow Example

This example demonstrates a two-stage workflow:
1. Planning Agent: Analyzes the task and creates a detailed implementation plan
2. Execution Agent: Implements the plan with full editing capabilities

The task: Create a Python web scraper that extracts article titles and URLs
from a news website, handles rate limiting, and saves results to JSON.
"""

import os
import tempfile
from pathlib import Path

from pydantic import SecretStr

from faheemcode.sdk import LLM, Conversation
from faheemcode.sdk.llm import content_to_str
from faheemcode.tools.preset.default import get_default_agent
from faheemcode.tools.preset.planning import get_planning_agent

def get_event_content(event):
    """Extract content from an event."""
    if hasattr(event, "llm_message"):
        return "".join(content_to_str(event.llm_message.content))
    return str(event)

"""Run the planning agent workflow example."""

# Create a temporary workspace
workspace_dir = Path(tempfile.mkdtemp())
print(f"Working in: {workspace_dir}")

# Configure LLM
api_key = os.getenv("LLM_API_KEY")
assert api_key is not None, "LLM_API_KEY environment variable is not set."
model = os.getenv("LLM_MODEL", "anthropic/claude-sonnet-4-5-20250929")
base_url = os.getenv("LLM_BASE_URL")
llm = LLM(
    model=model,
    base_url=base_url,
    api_key=SecretStr(api_key),
    usage_id="agent",
)

# Task description
task = """
Create a Python web scraper with the following requirements:
- Scrape article titles and URLs from a news website
- Handle HTTP errors gracefully with retry logic
- Save results to a JSON file with timestamp
- Use requests and BeautifulSoup for scraping

Do NOT ask for any clarifying questions. Directly create your implementation plan.
"""

print("=" * 80)
print("PHASE 1: PLANNING")
print("=" * 80)

# Create Planning Agent with read-only tools
planning_agent = get_planning_agent(llm=llm)

# Create conversation for planning
planning_conversation = Conversation(
    agent=planning_agent,
    workspace=str(workspace_dir),
)

# Run planning phase
print("Planning Agent is analyzing the task and creating implementation plan...")
planning_conversation.send_message(
    f"Please analyze this web scraping task and create a detailed "
    f"implementation plan:\n\n{task}"
)
planning_conversation.run()

print("\n" + "=" * 80)
print("PLANNING COMPLETE")
print("=" * 80)
print(f"Implementation plan saved to: {workspace_dir}/PLAN.md")

print("\n" + "=" * 80)
print("PHASE 2: EXECUTION")
print("=" * 80)

# Create Execution Agent with full editing capabilities
execution_agent = get_default_agent(llm=llm, cli_mode=True)

# Create conversation for execution
execution_conversation = Conversation(
    agent=execution_agent,
    workspace=str(workspace_dir),
)

# Prepare execution prompt with reference to the plan file
execution_prompt = f"""
Please implement the web scraping project according to the implementation plan.

The detailed implementation plan has been created and saved at: {workspace_dir}/PLAN.md

Please read the plan from PLAN.md and implement all components according to it.

Create all necessary files, implement the functionality, and ensure everything
works together properly.
"""

print("Execution Agent is implementing the plan...")
execution_conversation.send_message(execution_prompt)
execution_conversation.run()

# Get the last message from the conversation
execution_result = execution_conversation.state.events[-1]

print("\n" + "=" * 80)
print("EXECUTION RESULT:")
print("=" * 80)
print(get_event_content(execution_result))

print("\n" + "=" * 80)
print("WORKFLOW COMPLETE")
print("=" * 80)
print(f"Project files created in: {workspace_dir}")

# List created files
print("\nCreated files:")
for file_path in workspace_dir.rglob("*"):
    if file_path.is_file():
        print(f"  - {file_path.relative_to(workspace_dir)}")

# Report cost
cost = llm.metrics.accumulated_cost
print(f"EXAMPLE_COST: {cost}")

You can run the example code as-is.

Bring your own provider key
export LLM_API_KEY="your-api-key"
export LLM_MODEL="anthropic/claude-sonnet-4-5-20250929"  # or openai/gpt-4o, etc.
cd software-agent-sdk
uv run python examples/01_standalone_sdk/24_planning_agent_workflow.py
Faheem Code Cloud key
# https://app.faheemcode.ai/settings/api-keys
export LLM_API_KEY="example-user-api-key"
export LLM_MODEL="faheemcode/claude-sonnet-4-5-20250929"
cd software-agent-sdk
uv run python examples/01_standalone_sdk/24_planning_agent_workflow.py

Anatomy of a custom agent​

The planning agent demonstrates the two key components for creating specialized agent:

1. Custom tool selection​

Choose tools that match your agent's specific role. Here's how the planning agent defines its tools:


def register_planning_tools() -> None:
    """Register the planning agent tools."""
    from faheemcode.tools.glob import GlobTool
    from faheemcode.tools.grep import GrepTool
    from faheemcode.tools.planning_file_editor import PlanningFileEditorTool

    register_tool("GlobTool", GlobTool)
    logger.debug("Tool: GlobTool registered.")
    register_tool("GrepTool", GrepTool)
    logger.debug("Tool: GrepTool registered.")
    register_tool("PlanningFileEditorTool", PlanningFileEditorTool)
    logger.debug("Tool: PlanningFileEditorTool registered.")

def get_planning_tools() -> list[Tool]:
    """Get the planning agent tool specifications.

    Returns:
        List of tools optimized for planning and analysis tasks, including
        file viewing and PLAN.md editing capabilities for advanced
        code discovery and navigation.
    """
    register_planning_tools()

    return [
        Tool(name="GlobTool"),
        Tool(name="GrepTool"),
        Tool(name="PlanningFileEditorTool"),
    ]

The planning agent uses:

  • GlobTool: For discovering files and directories matching patterns
  • GrepTool: For searching specific content across files
  • PlanningFileEditorTool: For writing structured plans to PLAN.md only

This read-only approach (except for PLAN.md) keeps the agent focused on analysis without implementation distractions.

2. System prompt customization​

Custom agents can use specialized system prompts to guide behavior. The planning agent uses system_prompt_planning.j2 with injected plan structure that enforces:

  1. Objective: Clear goal statement
  2. Context Summary: Relevant system components and constraints
  3. Approach Overview: High-level strategy and rationale
  4. Implementation Steps: Detailed step-by-step execution plan
  5. Testing and Validation: Verification methods and success criteria

Complete implementation reference​

For a complete implementation example showing all these components working together, refer to the planning agent preset source code.

Next steps​