Copyright	(c) 2025 Tushar Adhatrao
License	MIT
Maintainer	Tushar Adhatrao <tusharadhatrao@gmail.com>
Safe Haskell	Safe-Inferred
Language	Haskell2010

Langchain.Agents.React

Description

Implements the ReAct pattern where the agent alternates between:

Reasoning (generating thoughts)
Acting (executing tools)

Example agent interaction:

agent <- createReactAgent llm [wikipediaTool, calculatorTool]
result <- runAgentExecutor executor "What's the population of Paris?"
-- Agent might:
-- 1. Use Wikipedia tool to find current population data
-- 2. Use calculator tool to verify numbers
-- 3. Return final answer

Synopsis

newtype ReactAgentOutputParser = ReactAgentOutputParser AgentStep
parseReactOutput :: Text -> Either String ReactAgentOutputParser
data LLM llm => ReactAgent llm = ReactAgent {
- reactLLM :: llm
- reactTools :: [AnyTool]
- reactPromptTemplate :: PromptTemplate
}
createReactAgent :: LLM llm => llm -> [AnyTool] -> IO (Either String (ReactAgent llm))
formatToolDescriptions :: [AnyTool] -> Text
formatToolNames :: [AnyTool] -> Text
getLastUserInput :: ChatMessage -> Text

Documentation

newtype ReactAgentOutputParser Source #

Output parser for ReAct agent responses Handles two primary formats:

Final answers containing "Final Answer:"
Action requests with "Action:" and "Action Input:"

Example parsing:

parseReactOutput "Final Answer: 42"
-- Right (Finish ...)

parseReactOutput "Action: calculator\nAction Input: 5+3"
-- Right (Continue ...)

Constructors

ReactAgentOutputParser AgentStep

Instances

Instances details

OutputParser ReactAgentOutputParser Source #
Instance details Defined in Langchain.Agents.React Methods parse :: Text -> Either String ReactAgentOutputParser Source #

parseReactOutput :: Text -> Either String ReactAgentOutputParser Source #

Parses the output from a React agent

data LLM llm => ReactAgent llm Source #

Core ReAct agent configuration. Contains:

LLM for reasoning
Available tools
Prompt template for interaction

Example creation:

agent <- createReactAgent
  openAIGPT
  [ AnyTool wikipediaTool
  , AnyTool calculatorTool
  ]

Constructors

ReactAgent
Fields reactLLM :: llm reactTools :: [AnyTool] reactPromptTemplate :: PromptTemplate

Instances

Instances details

LLM llm => Agent (ReactAgent llm) Source #
Instance details Defined in Langchain.Agents.React Methods planNextAction :: BaseMemory m => ReactAgent llm -> AgentState m -> IO (Either String AgentStep) Source # agentPrompt :: ReactAgent llm -> IO PromptTemplate Source # agentTools :: ReactAgent llm -> IO [AnyTool] Source #

createReactAgent :: LLM llm => llm -> [AnyTool] -> IO (Either String (ReactAgent llm)) Source #

Creates a ReAct agent with standard prompt structure The prompt instructs the LLM to:

List available tools
Follow thought-action-observation pattern
Provide final answers

Example prompt excerpt:

"Use the following format:
Thought: ...
Action: [tool_name]
Action Input: ..."

formatToolDescriptions :: [AnyTool] -> Text Source #

Formats tool descriptions for LLM consumption Creates a list like:

"Tool: wikipedia
 Description: Search Wikipedia..."

formatToolNames :: [AnyTool] -> Text Source #

Creates comma-separated tool names for prompt inclusion Example output: "wikipedia, calculator, weather"

getLastUserInput :: ChatMessage -> Text Source #

Extracts latest user query from chat history Handles cases where:

Multiple user messages exist
No user input found