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Choosing the Right Building Block

Multiple building blocks, three layers — but which ones does your workflow actually need? This page gives you comparison tables to quickly differentiate the blocks and a decision guide to match your situation to the right starting point.

Most workflows need just two or three blocks. The goal isn’t to use them all — it’s to pick the right ones for the job.

All blocks in one view — use this to quickly orient yourself, then drill into the layer tables below for full details.

BlockPrimary JobBest ForTypical User
ModelProcess and generateChoosing the right engine for speed, depth, or costEveryone
ContextInformGrounding the model in your specific domain knowledgeEveryone
ProjectOrganizePersisting instructions and context across conversationsEveryone
MemoryRememberAccumulating preferences and patterns over timeEveryone
PromptInstructOne-off or conversational tasks with clear instructionsEveryone
SkillStandardizeRepeatable routines you run the same way every timeEveryone
AgentExecute autonomouslyMulti-step workflows requiring planning and tool usePower user
MCPConnectBridging AI to external tools, data, and servicesPower user
APIIntegrate programmaticallyEmbedding AI in applications and automated pipelinesDeveloper
SDKOrchestrate in codeBuilding agent systems with tool use, memory, and handoffsDeveloper
CLIInteract from terminalWorking with AI in the terminal, scripting, and headless automationPower user / Developer

The persistent foundation: engine, knowledge, and workspace powering every interaction.

ModelContextProjectMemory
What it providesAI engine that processes inputs and generates outputsBackground knowledge the model doesn’t havePersistent workspace grouping instructions, context, and skillsAccumulated knowledge from past interactions
Primary jobProcess and generateInformOrganizeRemember
PersistenceAlways available (platform-managed)Ephemeral (per-conversation) or attached to a projectPersistent across conversationsPersistent and growing across conversations
ContainsTrained weights, capability tiers, modality supportFiles, docs, data, examples, reference materialInstructions, context files, conversation history, skillsPreferences, decisions, facts, learned patterns
When it loadsSelected before or during a conversationAttached at conversation start or mid-conversationActive when you open a conversation in the projectRetrieved automatically when relevant
Can include codeNo (model selection, not authoring)Yes (code files as reference material)Yes (code in project knowledge or instructions)No (system-managed, natural language)
Best forChoosing the right engine for speed, depth, or costGrounding the model in your specific domainPersisting setup so you don’t re-upload every timeAdapting AI behavior over time without manual setup
Who manages itPlatform (you choose tier)User-curatedUser-curatedSystem-managed
Requires external accessNoNo (you bring the files)NoNo
Typical userEveryoneEveryoneEveryoneEveryone

The execution layer: instructions, routines, and autonomous agents that direct and do the work.

PromptSkillAgent
What it providesNatural language instructions to the modelReusable routine with defined inputs and outputsAutonomous AI that plans, uses tools, and executes multi-step work
Primary jobInstructStandardizeExecute autonomously
PersistenceEphemeral (per-conversation)Persistent (saved as files, reusable across conversations)Ephemeral (runs for a session) or scheduled
ContainsNatural language instructions, examples, constraintsInstructions, reference files, output format specsGoals, tool access, planning logic, decision-making
When it loadsWhen you type or send a messageAuto-triggered when relevant, or invoked via slash commandLaunched explicitly or on a schedule
Can include codeNo (natural language only)Yes (scripts, templates, code references)Yes (reads, writes, and runs code)
Best forOne-off or conversational tasks with clear instructionsRepeatable routines you run the same way every timeMulti-step workflows requiring planning and tool use
Who manages itUser (typed in the moment)User-curated (packaged for reuse)User-launched or developer-built
Requires external accessNoNo (self-contained instructions)Often yes (uses tools, files, MCP connections)
Typical userEveryoneEveryonePower user

The connection layer: protocols, interfaces, and frameworks that bridge AI to external systems and code.

MCPAPISDKCLI
What it providesConnector to external tools, services, and databasesProgrammatic interface for accessing AI modelsFrameworks for building AI workflows in codeTerminal-native interface for interacting with AI
Primary jobConnectIntegrate programmaticallyOrchestrate in codeInteract from terminal
PersistencePersistent (configured once, available across conversations)Stateless (each call is independent)Persistent (code you deploy and maintain)Persistent (project memory files, settings)
ContainsServer configs, tool definitions, authenticationAPI keys, endpoint URLs, request/response schemasLibraries, agent loops, tool abstractions, patternsSkills, plugins, hooks, MCP connections, project memory
When it loadsConnected at startup or configured in settingsCalled on demand from codeImported into your application codeLaunched from the terminal interactively or via script
Can include codeYes (server implementations)Yes (code making HTTP requests)Yes (the primary interface is code)Yes (reads, writes, and runs code)
Best forBridging AI to external tools, data, and servicesEmbedding AI in applications and automated pipelinesBuilding agent systems with tool use, memory, and handoffsWorking with AI in the terminal, scripting, headless automation
Who manages itUser-configured or developer-builtDeveloper-ownedDeveloper-ownedUser-launched or script-driven
Requires external accessYes (bridges to external systems)Yes (calls external APIs)Yes (wraps APIs and external services)Yes (calls APIs under the hood)
Typical userPower userDeveloperDeveloperPower user / Developer

Use this table to find your starting point. Most real workflows combine several blocks — this tells you where to begin.

I want to…Start withAdd when needed
Ask AI a questionPrompt+ Context if it needs your specific data
Get better answers about my domainContext + Prompt+ Project to persist the setup
Stop re-uploading the same filesProject+ Memory to also retain learned preferences
Have AI remember how I like things doneMemoryAlready persistent — just keep using it
Run the same workflow every weekSkill+ MCP if the skill needs external data
Pull live data into a conversationMCP+ Skill to standardize what you do with the data
Automate a multi-step research taskAgent+ MCP for external sources, + Skill for sub-routines
Build AI into my appAPI+ SDK for complex orchestration
Coordinate multiple agents in codeSDK+ MCP for external tool access
Work with AI in my terminalCLI+ Skills for reusable routines, + MCP for external data
Automate AI in shell scripts or CICLI (headless mode)+ MCP for external system access
Get AI help while codingCLI+ Project memory for persistent conventions
Choose between fast and deep AIModel (select the right tier)All other blocks work with any model