Class LangChainMCPAgent

constructor

• new LangChainMCPAgent(options: MCPAgentOptions): LangChainMCPAgent

  Creates a LangChain MCP agent.

  Parameters

  • options: MCPAgentOptions

    Model, MCP servers, tools, and execution settings.

  Returns LangChainMCPAgent

  Throws

  Error if local execution does not include a model and MCP client, connectors, or server configurations.

observabilityManager

toolsUsedNames

clearConversationHistory

• clearConversationHistory(): void

  Clears stored history, retaining the system message when memory is enabled.

  Returns void

close

• close(): Promise<void>

  Flushes observability, closes owned MCP resources, and resets the executor.

  Returns Promise<void>

flush

• flush(): Promise<void>

  Flush observability traces to the configured observability platform. Important for serverless environments where traces need to be sent before function termination.

  Returns Promise<void>

getConversationHistory

• getConversationHistory(): BaseMessage[]

  Returns BaseMessage[]

  A shallow copy of the stored LangChain message history.

getDisallowedTools

• getDisallowedTools(): string[]

  Returns string[]

  The configured MCP tool denylist.

getMetadata

• getMetadata(): Record<string, any>

  Get current metadata

  Returns Record<string, any>

  A copy of the current metadata object

getSystemMessage

• getSystemMessage(): SystemMessage<MessageStructure<MessageToolSet>> | null

  Returns SystemMessage<MessageStructure<MessageToolSet>> | null

  The current LangChain system message, or null before creation.

getTags

• getTags(): string[]

  Get current tags

  Returns string[]

  A copy of the current tags array

initialize

• initialize(): Promise<void>

  Creates configured clients and models, connects MCP servers, loads tools, and builds the LangChain executor.

  Returns Promise<void>

  Throws

  Error if a configured model or MCP server cannot be initialized.

prettyStreamEvents

• prettyStreamEvents(options: RunOptions): AsyncGenerator<void, string, void>

  Yields with pretty-printed output for code mode with options object.

  Parameters

  • options: RunOptions

  Returns AsyncGenerator<void, string, void>

• prettyStreamEvents<T>(
      options: RunOptions<T>,
  ): AsyncGenerator<void, string, void>

  Yields with pretty-printed output for code mode with options object and structured output.

  Type Parameters

  • T

  Parameters

  • options: RunOptions<T>

  Returns AsyncGenerator<void, string, void>

• prettyStreamEvents<T = string>(
      query: string,
      maxSteps?: number,
      manageConnector?: boolean,
      externalHistory?: BaseMessage[],
      outputSchema?: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>,
  ): AsyncGenerator<void, string, void>

  Yields with pretty-printed output for code mode. This method formats and displays tool executions in a user-friendly way with syntax highlighting.

  Type Parameters

  • T = string

  Parameters

  • query: string
  • OptionalmaxSteps: number
  • OptionalmanageConnector: boolean
  • OptionalexternalHistory: BaseMessage[]
  • OptionaloutputSchema: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>

  Returns AsyncGenerator<void, string, void>

  Deprecated

  Use the options object instead: prettyStreamEvents({ prompt, maxSteps, ... }).

run

• run(options: RunOptions): Promise<string>

  Runs the agent with options object and returns a promise for the final result.

  Parameters

  • options: RunOptions

  Returns Promise<string>

• run<T>(options: RunOptions<T>): Promise<T>

  Runs the agent with options object and structured output, returns a promise for the typed result.

  Type Parameters

  • T

  Parameters

  • options: RunOptions<T>

  Returns Promise<T>

• run(
      query: string,
      maxSteps?: number,
      manageConnector?: boolean,
      externalHistory?: BaseMessage[],
      outputSchema?: undefined,
      signal?: AbortSignal,
  ): Promise<string>

  Runs the agent and returns a promise for the final result.

  Parameters

  • query: string
  • OptionalmaxSteps: number
  • OptionalmanageConnector: boolean
  • OptionalexternalHistory: BaseMessage[]
  • OptionaloutputSchema: undefined
  • Optionalsignal: AbortSignal

  Returns Promise<string>

  Deprecated

  Use the options object instead: run({ prompt, maxSteps, ... }).

• run<T>(
      query: string,
      maxSteps?: number,
      manageConnector?: boolean,
      externalHistory?: BaseMessage[],
      outputSchema?: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>,
      signal?: AbortSignal,
  ): Promise<T>

  Runs the agent with structured output and returns a promise for the typed result.

  Type Parameters

  • T

  Parameters

  • query: string
  • OptionalmaxSteps: number
  • OptionalmanageConnector: boolean
  • OptionalexternalHistory: BaseMessage[]
  • OptionaloutputSchema: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>
  • Optionalsignal: AbortSignal

  Returns Promise<T>

  Deprecated

  Use the options object instead: run({ prompt, schema, maxSteps, ... }).

setDisallowedTools

• setDisallowedTools(disallowedTools: string[]): void

  Replaces the tool denylist for the next initialization.

  Parameters

  • disallowedTools: string[]

    MCP tool names to omit.

  Returns void

setMetadata

• setMetadata(newMetadata: Record<string, any>): void

  Set metadata for observability traces

  Parameters

  • newMetadata: Record<string, any>

    Key-value pairs to add to metadata. Keys should be strings, values should be serializable.

  Returns void

setSystemMessage

• setSystemMessage(message: string): void

  Replaces the system instruction and rebuilds an initialized executor.

  Parameters

  • message: string

    New system instruction.

  Returns void

setTags

• setTags(newTags: string[]): void

  Set tags for observability traces

  Parameters

  • newTags: string[]

    Array of tag strings to add. Duplicates will be automatically removed.

  Returns void

stream

• stream(options: RunOptions): AsyncGenerator<LangChainAgentStep, string, void>

  Streams the agent execution with options object and returns string result.

  Parameters

  • options: RunOptions

  Returns AsyncGenerator<LangChainAgentStep, string, void>

• stream<T>(options: RunOptions<T>): AsyncGenerator<LangChainAgentStep, T, void>

  Streams the agent execution with options object and structured output.

  Type Parameters

  • T

  Parameters

  • options: RunOptions<T>

  Returns AsyncGenerator<LangChainAgentStep, T, void>

• stream<T = string>(
      query: string,
      maxSteps?: number,
      manageConnector?: boolean,
      externalHistory?: BaseMessage[],
      outputSchema?: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>,
      signal?: AbortSignal,
  ): AsyncGenerator<LangChainAgentStep, string | T, void>

  Streams the agent execution and yields agent steps.

  Type Parameters

  • T = string

  Parameters

  • query: string
  • OptionalmaxSteps: number
  • OptionalmanageConnector: boolean
  • OptionalexternalHistory: BaseMessage[]
  • OptionaloutputSchema: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>
  • Optionalsignal: AbortSignal

  Returns AsyncGenerator<LangChainAgentStep, string | T, void>

  Deprecated

  Use the options object instead: stream({ prompt, maxSteps, ... }).

streamEvents

• streamEvents(options: RunOptions): AsyncGenerator<StreamEvent, void, void>

  Yields LangChain StreamEvent objects with options object.

  Parameters

  • options: RunOptions

  Returns AsyncGenerator<StreamEvent, void, void>

• streamEvents<T>(options: RunOptions<T>): AsyncGenerator<StreamEvent, void, void>

  Yields LangChain StreamEvent objects with options object and structured output.

  Type Parameters

  • T

  Parameters

  • options: RunOptions<T>

  Returns AsyncGenerator<StreamEvent, void, void>

• streamEvents<T = string>(
      query: string,
      maxSteps?: number,
      manageConnector?: boolean,
      externalHistory?: BaseMessage[],
      outputSchema?: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>,
      signal?: AbortSignal,
  ): AsyncGenerator<StreamEvent, void, void>

  Yields LangChain StreamEvent objects from the underlying streamEvents() method. This provides token-level streaming and fine-grained event updates.

  Type Parameters

  • T = string

  Parameters

  • query: string
  • OptionalmaxSteps: number
  • OptionalmanageConnector: boolean
  • OptionalexternalHistory: BaseMessage[]
  • OptionaloutputSchema: ZodType<T, unknown, $ZodTypeInternals<T, unknown>>
  • Optionalsignal: AbortSignal

  Returns AsyncGenerator<StreamEvent, void, void>

  Deprecated

  Use the options object instead: streamEvents({ prompt, maxSteps, ... }).

StaticgetPackageVersion

• getPackageVersion(): string

  Get the mcp-use package version. Works in all environments (Node.js, browser, Cloudflare Workers, Deno, etc.)

  Returns string