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Effect provides a comprehensive, provider-agnostic framework for building AI applications with large language models (LLMs). The AI modules in effect/unstable/ai offer a unified interface that works across multiple providers while maintaining full type safety and Effect’s composable architecture.

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Core Modules

The Effect AI framework consists of several key modules:
  • LanguageModel - Unified interface for text generation, structured output, and streaming
  • Chat - Stateful conversation sessions with automatic history management
  • Tool - Define tools that AI models can call to extend their capabilities
  • Toolkit - Group tools together and implement handlers
  • Prompt - Build and combine prompts with rich content types
  • Response - Type-safe response parsing with text, tool calls, and metadata

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Supported Providers

Effect AI currently supports the following providers through dedicated packages:
  • OpenAI - @effect/ai-openai - GPT models, code interpreter, file search, web search
  • Anthropic - @effect/ai-anthropic - Claude models, computer use, bash execution
  • OpenAI-compatible - @effect/ai-openai-compat - Any OpenAI-compatible API
  • OpenRouter - @effect/ai-openrouter - Access to multiple models through OpenRouter

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Why Effect AI?

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Provider-Agnostic Interface

Write your AI logic once and switch providers without changing your code: 
import { Effect, Layer } from "effect"
import { LanguageModel } from "effect/unstable/ai"
import { OpenAiLanguageModel } from "@effect/ai-openai"
import { AnthropicLanguageModel } from "@effect/ai-anthropic"

// Your AI logic is decoupled from the provider
const generateSummary = (text: string) =>
  LanguageModel.generateText({
    prompt: `Summarize this text: ${text}`
  })

// Switch providers by changing the layer
const withOpenAI = generateSummary("...").pipe(
  Effect.provide(OpenAiLanguageModel.model("gpt-4"))
)

const withClaude = generateSummary("...").pipe(
  Effect.provide(AnthropicLanguageModel.model("claude-3-5-sonnet"))
)

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Type-Safe Tools and Structured Output

Define tools with schemas and get automatic validation: 
import { Schema } from "effect"
import { Tool } from "effect/unstable/ai"

const GetWeather = Tool.make("GetWeather", {
  description: "Get current weather for a location",
  parameters: Schema.Struct({
    location: Schema.String,
    units: Schema.Literals("celsius", "fahrenheit")
  }),
  success: Schema.Struct({
    temperature: Schema.Number,
    condition: Schema.String,
    humidity: Schema.Number
  })
})

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Effect Integration

Leverage Effect’s full ecosystem:
  • Error handling - Semantic errors with retry logic
  • Telemetry - OpenTelemetry integration out of the box
  • Streaming - First-class streaming support with Stream
  • Concurrency - Control tool call execution with concurrency options
  • Resource management - Automatic cleanup with Scope

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Fallback Strategies

Build resilient AI applications with ExecutionPlan: 
import { ExecutionPlan } from "effect"
import { OpenAiLanguageModel } from "@effect/ai-openai"
import { AnthropicLanguageModel } from "@effect/ai-anthropic"

const plan = ExecutionPlan.make(
  {
    provide: OpenAiLanguageModel.model("gpt-4-mini"),
    attempts: 3
  },
  {
    provide: AnthropicLanguageModel.model("claude-3-5-sonnet"),
    attempts: 2
  }
)

const resilientGeneration = LanguageModel.generateText({
  prompt: "Write a haiku about programming"
}).pipe(
  Effect.withExecutionPlan(plan)
)

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Basic Example

Here’s a complete example showing text generation, structured output, and tool calling: 
import { Effect, Schema, Layer, Config } from "effect"
import { LanguageModel, Tool, Toolkit } from "effect/unstable/ai"
import { OpenAiClient, OpenAiLanguageModel } from "@effect/ai-openai"
import { FetchHttpClient } from "effect/unstable/http"

// Setup OpenAI client
const OpenAiClientLayer = OpenAiClient.layerConfig({
  apiKey: Config.redacted("OPENAI_API_KEY")
}).pipe(Layer.provide(FetchHttpClient.layer))

// Define a tool
const Calculator = Tool.make("Calculator", {
  description: "Perform arithmetic operations",
  parameters: Schema.Struct({
    operation: Schema.Literals("add", "subtract", "multiply", "divide"),
    a: Schema.Number,
    b: Schema.Number
  }),
  success: Schema.Number
})

// Create toolkit with handlers
const toolkit = Toolkit.make(Calculator)
const toolkitLayer = toolkit.toLayer(
  Effect.succeed(
    toolkit.of({
      Calculator: ({ operation, a, b }) => {
        switch (operation) {
          case "add": return Effect.succeed(a + b)
          case "subtract": return Effect.succeed(a - b)
          case "multiply": return Effect.succeed(a * b)
          case "divide": return Effect.succeed(a / b)
        }
      }
    })
  )
)

// Use the language model
const program = Effect.gen(function*() {
  // Simple text generation
  const textResponse = yield* LanguageModel.generateText({
    prompt: "Explain quantum computing in one sentence"
  })
  console.log(textResponse.text)

  // Structured output
  const ContactSchema = Schema.Struct({
    name: Schema.String,
    email: Schema.String
  })
  const structured = yield* LanguageModel.generateObject({
    prompt: "Extract: John Doe, [email protected]",
    schema: ContactSchema
  })
  console.log(structured.value)

  // Tool calling
  const tk = yield* toolkit
  const toolResponse = yield* LanguageModel.generateText({
    prompt: "What is 42 multiplied by 7?",
    toolkit: tk
  })
  console.log(toolResponse.text)
  console.log("Tool calls:", toolResponse.toolCalls.length)
})

const runnable = program.pipe(
  Effect.provide(OpenAiLanguageModel.model("gpt-4")),
  Effect.provide(toolkitLayer),
  Effect.provide(OpenAiClientLayer)
)

​
Error Handling

Effect AI provides semantic error types through AiError: 
import { Effect, Match } from "effect"
import { AiError, LanguageModel } from "effect/unstable/ai"

const handleErrors = LanguageModel.generateText({
  prompt: "Hello!"
}).pipe(
  Effect.catchAll((error) =>
    Match.type<AiError.AiError>().pipe(
      Match.when(
        { reason: { _tag: "RateLimitError" } },
        (err) => Effect.logWarning(`Rate limited: ${err.reason.retryAfter}`)
      ),
      Match.when(
        { reason: { _tag: "AuthenticationError" } },
        (err) => Effect.fail(new Error("Invalid API key"))
      ),
      Match.when(
        { reason: { isRetryable: true } },
        (err) => Effect.retry(/* retry options */)
      ),
      Match.orElse((err) => Effect.fail(err))
    )(error)
  )
)

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Next Steps

Language Models

Learn about text generation, structured output, and streaming

Tools & Chat

Build AI agents with tools and stateful conversations

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