Block Schemas

This section contains the complete YAML schema definitions for all available block types in Sim Studio. Each block type has specific configuration requirements and output formats.

Core Blocks

These are the essential building blocks for creating workflows:

Starter Block

Workflow entry point supporting manual triggers, webhooks, and schedules

Agent Block

AI-powered processing with LLM integration and tool support

Function Block

Custom JavaScript/TypeScript code execution environment

Response Block

Format and return final workflow results

Logic & Control Flow

Blocks for implementing conditional logic and control flow:

Condition Block

Conditional branching based on boolean expressions

Router Block

AI-powered intelligent routing to multiple paths

Loop Block

Iterative processing with for and forEach loops

Parallel Block

Concurrent execution across multiple instances

Integration Blocks

Blocks for connecting to external services and systems:

API Block

HTTP requests to external REST APIs

Webhook Block

Webhook triggers for external integrations

Advanced Blocks

Specialized blocks for complex workflow patterns:

Evaluator Block

Validate outputs against defined criteria and metrics

Workflow Block

Execute other workflows as reusable components

Common Schema Elements

All blocks share these common elements:

Basic Structure

block-id:
  type: <block-type>
  name: <display-name>
  inputs:
    # Block-specific configuration
  connections:
    # Connection definitions

Connection Types

success: Target block for successful execution
error: Target block for error handling (optional)
conditions: Multiple paths for conditional blocks

Environment Variables

Use double curly braces for environment variables:

inputs:
  apiKey: '{{API_KEY_NAME}}'
  endpoint: '{{SERVICE_ENDPOINT}}'

Block References

Reference other block outputs using the block name in lowercase:

inputs:
  userPrompt: <blockname.content>
  data: <functionblock.output>
  originalInput: <start.input>

Validation Rules

All YAML blocks are validated against their schemas:

Required fields: Must be present
Type validation: Values must match expected types
Enum validation: String values must be from allowed lists
Range validation: Numbers must be within specified ranges
Pattern validation: Strings must match regex patterns (where applicable)

Quick Reference

Block Types and Properties

Block Type	Primary Output	Common Use Cases
starter	`.input`	Workflow entry point
agent	`.content`	AI processing, text generation
function	`.output`	Data transformation, calculations
api	`.output`	External service integration
condition	N/A (branching)	Conditional logic
router	N/A (branching)	Intelligent routing
response	N/A (terminal)	Final output formatting
loop	`.results`	Iterative processing
parallel	`.results`	Concurrent processing
webhook	`.payload`	External triggers
evaluator	`.score`	Output validation, quality assessment
workflow	`.output`	Sub-workflow execution, modularity

Required vs Optional

Always required: type, name
Usually required: inputs, connections
Context dependent: Specific input fields vary by block type
Always optional: error connections, UI-specific fields