Blocks

Blocks are the building components you connect together to create AI workflows. Think of them as specialized modules that each handle a specific task—from chatting with AI models to making API calls or processing data.

Core Block Types

Sim provides seven core block types that handle the essential functions of AI workflows:

Processing Blocks

• Agent - Chat with AI models (OpenAI, Anthropic, Google, local models)
• Function - Run custom JavaScript/TypeScript code
• API - Connect to external services via HTTP requests

Logic Blocks

• Condition - Branch workflow paths based on boolean expressions
• Router - Use AI to intelligently route requests to different paths
• Evaluator - Score and assess content quality using AI

Output Blocks

• Response - Format and return final results from your workflow

How Blocks Work

Each block has three main components:

Inputs: Data coming into the block from other blocks or user input Configuration: Settings that control how the block behaves Outputs: Data the block produces for other blocks to use

Connecting Blocks

You create workflows by connecting blocks together. The output of one block becomes the input of another:

• Drag to connect: Drag from an output port to an input port
• Multiple connections: One output can connect to multiple inputs
• Branching paths: Some blocks can route to different paths based on conditions

Common Patterns

Sequential Processing

Connect blocks in a chain where each block processes the output of the previous one:

User Input → Agent → Function → Response

Conditional Branching

Use Condition or Router blocks to create different paths:

User Input → Router → Agent A (for questions)
                   → Agent B (for commands)

Quality Control

Use Evaluator blocks to assess and filter outputs:

Agent → Evaluator → Condition → Response (if good)
                              → Agent (retry if bad)

Block Configuration

Each block type has specific configuration options:

All Blocks:

• Input/output connections
• Error handling behavior
• Execution timeout settings

AI Blocks (Agent, Router, Evaluator):

• Model selection (OpenAI, Anthropic, Google, local)
• API keys and authentication
• Temperature and other model parameters
• System prompts and instructions

Logic Blocks (Condition, Function):

• Custom expressions or code
• Variable references
• Execution environment settings

Integration Blocks (API, Response):

• Endpoint configuration
• Headers and authentication
• Request/response formatting