Phase 3 · Agentic
AI Agents
Build systems where models can decide what to do next, use tools, maintain state, recover from failures, and collaborate with other agents. Planning · tools · MCP · memory · multi-agent · LangGraph.
Short on time? Do the 27-day version in 100 Days of AI EngineeringOne of the hottest topics in current job descriptions. Tool calling, MCP, LangGraph, and multi-agent setups are keywords that pass resume filters and come up often in interviews.
More and more common, but many production tasks are better handled by simple fixed workflows. Knowing when not to build an agent is part of the skill.
Modules 11
01 What is an agent? M5.1 1
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The agent loop
Understand the basic loop: goal → decide → act → observe → repeat → finish.
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Call vs chain vs workflow vs agent
Distinguish LLM call vs chain vs workflow vs agent, especially based on who decides what happens next.
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Where agents are useful
Understand where agents are useful: open-ended, multi-step tasks where the execution path cannot be fully predetermined.
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When a workflow is better
Know when a deterministic workflow is simpler, cheaper, and more reliable.
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The components of an agent
Understand the basic components of an agent: model, instructions, tools, state/memory, control loop, stopping conditions.
Outcome · Decide whether a problem genuinely requires an agent.
02 ReAct, planning & reflection M5.2 2
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The ReAct pattern
Understand the ReAct pattern: the agent alternates between deciding what to do and acting on the environment.
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Writing the loop by hand first
Implement a simple agent loop manually before using a framework.
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Step-by-step vs plan-first
Understand step-by-step execution vs plan-first execution.
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Decomposing and revising plans
Break complex goals into subtasks and dynamically revise plans as new information appears.
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Reflection & self-correction
Use reflection/self-correction when actions fail or results are insufficient.
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Stopping conditions & loop protection
Implement stopping conditions, maximum steps, and protection against repetitive loops.
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What planning costs
Understand that more planning/reflection can increase quality but also latency and cost.
Outcome · Build an agent capable of solving a multi-step task without hard-coding its exact execution path.
03 Tools for agents M5.3 2
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From tool calling to agentic tool use
Extend Level 2 tool calling into agentic tool use where the model repeatedly selects among available capabilities.
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Designing tools for agents
Design tools with clear names, descriptions, schemas, typed arguments, useful outputs, and useful error messages.
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Improving selection & arguments
Improve tool selection and argument correctness.
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Sequential, parallel & repeated calls
Handle sequential, dependent, parallel, and repeated tool calls.
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Recovering from tool failures
Handle tool failures and allow the agent to recover or choose an alternative.
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Limiting tool-result size
Limit the size of tool results returned to the model so context does not become overwhelmed.
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Read-only vs consequential tools
Separate read-only tools from consequential tools and add confirmation/permission checks where necessary.
Outcome · Give an agent useful capabilities without giving it uncontrolled access to the underlying application.
04 MCP (Model Context Protocol) M5.4 3
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Why MCP exists
Understand why MCP exists: provide a standardized way for AI applications to connect to external tools, resources, and prompts.
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Host → client → server
Understand the host → client → server architecture and the responsibility of each component.
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Tool calling vs MCP
Distinguish ordinary function calling from MCP: tool calling describes how a model requests an action, while MCP standardizes how external capabilities are exposed to AI applications.
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Building an MCP server
Build an MCP server that exposes tools/resources from a real system such as a database, filesystem, SaaS application, or internal API.
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Schemas, transports & auth
Work with schemas, capabilities, errors, local/remote transports, and authentication.
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Building and connecting a client
Build/use an MCP client and connect it to one or more servers.
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Permissions & untrusted servers
Understand permissions, trust boundaries, and the risk of connecting to untrusted MCP servers.
Outcome · Build a reusable MCP integration that can expose a real system to compatible AI applications.
05 Memory basics M5.5 2
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History, state, short- & long-term memory
Distinguish conversation history, state, short-term memory, and long-term memory.
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Short-term memory
Implement short-term memory so an agent can retain information during a conversation or task.
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Long-term memory
Implement basic long-term memory using persistent stores or retrieval-backed memory.
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Storing what is worth keeping
Store useful facts, preferences, summaries, or previous outcomes instead of blindly preserving every message.
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Retrieving only relevant memories
Retrieve relevant memories when needed rather than injecting the entire history into every request.
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Write → retrieve → update → forget
Understand basic memory operations: write → retrieve → update → forget.
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Trimming & summarizing growth
Handle growing conversations through trimming or summarization.
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Offloading comes later
Keep deeper context offloading/compression strategies for the later Context Engineering level.
Outcome · Build an agent that remembers relevant information during and across interactions.
06 Multi-agent architectures M5.6 3
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Why more than one agent
Understand why multiple agents may help when tasks require different tools, instructions, models, permissions, or areas of expertise.
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Common patterns
Learn common patterns:
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Orchestrator → workers
orchestrator → workers
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Sequential handoffs
sequential handoffs
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Parallel specialists
parallel specialists
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Hierarchical supervisor/worker
hierarchical supervisor/worker architectures.
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Building an orchestrator
Build an orchestrator that decomposes work and delegates tasks to specialist agents.
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Passing state & aggregating output
Pass useful state/context between agents and aggregate their outputs.
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Worker failure & escalation
Handle worker failures, retries, reassignment, and escalation.
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What goes wrong with many agents
Understand common multi-agent problems: duplicated work, coordination overhead, context growth, conflicting results, latency, and cost.
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A2A vs MCP
Understand A2A as an interoperability approach for independently built agents and contrast it conceptually with MCP: MCP connects agents to tools/resources; A2A connects agents to agents.
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When one strong agent is better
Learn when multiple agents genuinely improve specialization and when one strong agent with several tools is preferable.
Outcome · Design multi-agent systems only when decomposition or specialization actually justifies the additional complexity.
07 Building agents with LangGraph M5.7 3
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What LangGraph is for
LangGraph is positioned as a low-level orchestration framework/runtime for long-running, stateful agents.
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State, nodes & edges
Model agent execution using state, nodes, and edges.
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Building nodes
Build nodes for model calls, tools, processing logic, and decisions.
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Conditional edges
Use conditional edges to dynamically determine the next action.
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Loops for retries & iteration
Implement loops for repeated tool use, retries, and iterative execution.
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Checkpointing & persistence
Add checkpointing/persistence so execution can survive interruptions.
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Resuming long runs
Resume long-running agent runs rather than restarting them from scratch.
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Human-in-the-loop interrupts
Add human-in-the-loop interrupts for actions requiring approval or intervention.
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Inspecting state to debug
Inspect agent state to debug why a particular execution path was taken.
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When a graph beats a loop
Understand when graph-based orchestration offers more control than a simple agent loop.
Outcome · Build a controllable, stateful, resumable agent with explicit execution logic.
08 Sandboxed execution M5.8 1
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Why generated code must not run in-process
Understand why model-generated Python, shell commands, or arbitrary programs should not execute directly inside the production application.
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Sandboxes: E2B, Modal & containers
Run generated code inside isolated environments such as E2B, Modal, containers, or equivalent sandboxes.
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Restricting filesystem, network & time
Restrict filesystem, network, credentials, execution time, and compute resources.
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Capturing output safely
Capture stdout, stderr, files, and errors and return only necessary results to the agent.
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Reducing the blast radius
Understand the principle of reducing the blast radius when an agent can take executable actions.
Outcome · Give an agent code-execution capabilities without exposing the host system unnecessarily.
09 Agent reliability, UX & failure recovery M5.9 2
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Common agent failures
Handle common failures: wrong tool selection, bad arguments, unavailable tools, repeated actions, incomplete plans, infinite loops, and context growth.
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Step, time, retry & cost budgets
Define maximum steps, timeouts, retry budgets, cost/token budgets, and stopping conditions.
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Idempotent operations
Make operations idempotent where possible so retries do not accidentally repeat real-world side effects.
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Persisting state to resume
Persist enough execution state to resume after interruption.
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Fallbacks & human escalation
Add fallback actions and human escalation when the agent cannot continue safely.
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Surfacing progress to users
Surface useful progress to users: current task, tool/action being performed, results, sources, and requests for approval.
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Cancel, pause, resume, redirect
Allow users to cancel, pause, resume, or redirect long-running work.
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Understandable without exposing reasoning
Avoid exposing unnecessary private reasoning while still making execution understandable.
Outcome · Build agents that fail predictably, recover gracefully, and keep the user informed and in control.
10 Agent frameworks & libraries M5.10 2
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One agent, several frameworks
After learning the primitives, implement the same small agent in several frameworks and understand what each one abstracts.
LangGraph
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Graph-based, stateful orchestration
Low-level graph/state-based orchestration for long-running, stateful agents.
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Where explicit control flow wins
Strong fit when explicit control flow, persistence, loops, and human-in-the-loop behavior matter.
Google Agent Development Kit (ADK)
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Google's ADK
Build agents using Google's open-source ADK and explore its agent, session/state, tools, multi-agent, deployment, and A2A-related abstractions.
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Building, debugging & deploying agents
Understand its emphasis on building, debugging, evaluating, and deploying agent systems rather than merely wrapping an LLM call.
CrewAI
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Crews and Flows
Build agents and collaborative Crews, and understand Flows for more controlled workflow-style orchestration.
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Role-based vs graph orchestration
Explore role-based multi-agent patterns and compare them with explicit graph orchestration.
Agno
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Agents, Teams & Workflows
Build Agents, Teams, and Workflows and understand the distinction between agent autonomy, team coordination, and deterministic workflows.
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The production runtime layer
Explore its production/runtime layer and how agent systems can be exposed as services.
OpenAI Agents SDK
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Code-first agents with handoffs
Build code-first agents using tools, handoffs, sessions, guardrails, tracing, and specialist agents.
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Lightweight SDK vs graph frameworks
Compare a lightweight SDK-style agent loop with graph-oriented or multi-agent-first frameworks.
Compare them on
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Abstraction level
abstraction level
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Control over execution
control over execution
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State & persistence
state/persistence
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Multi-agent support
multi-agent support
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Tool integrations
tool integrations
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MCP & A2A support
MCP/A2A support
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Debugging & observability
debugging/observability
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Deployment
deployment
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Vendor & model flexibility
vendor/model flexibility.
Outcome · Understand the agent-framework landscape and choose a framework based on architecture rather than popularity.
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