Feature/MCP (Model Context Protocol) (#4134)

add mcp tools

packages/components/src/Interface.ts

@@ -167,6 +167,7 @@ export interface IUsedTool {
     toolInput: object
     toolOutput: string | object
     sourceDocuments?: ICommonObject[]
+    error?: string
 }
 
 export interface IMultiAgentNode {

packages/components/src/agents.ts

@@ -24,6 +24,7 @@ import {
 } from 'langchain/agents'
 import { formatLogToString } from 'langchain/agents/format_scratchpad/log'
 import { IUsedTool } from './Interface'
+import { getErrorMessage } from './error'
 
 export const SOURCE_DOCUMENTS_PREFIX = '\n\n----FLOWISE_SOURCE_DOCUMENTS----\n\n'
 export const ARTIFACTS_PREFIX = '\n\n----FLOWISE_ARTIFACTS----\n\n'
@@ -463,7 +464,21 @@ export class AgentExecutor extends BaseChain<ChainValues, AgentExecutorOutput> {
                                 throw e
                             }
                             observation = await new ExceptionTool().call(observation, runManager?.getChild())
+                            usedTools.push({
+                                tool: tool.name,
+                                toolInput: action.toolInput as any,
+                                toolOutput: '',
+                                error: getErrorMessage(e)
+                            })
                             return { action, observation: observation ?? '' }
+                        } else {
+                            usedTools.push({
+                                tool: tool.name,
+                                toolInput: action.toolInput as any,
+                                toolOutput: '',
+                                error: getErrorMessage(e)
+                            })
+                            return { action, observation: getErrorMessage(e) }
                         }
                     }
                     if (typeof observation === 'string' && observation.includes(SOURCE_DOCUMENTS_PREFIX)) {

packages/components/src/error.ts

@@ -0,0 +1,25 @@
+type ErrorWithMessage = {
+    message: string
+}
+
+const isErrorWithMessage = (error: unknown): error is ErrorWithMessage => {
+    return (
+        typeof error === 'object' && error !== null && 'message' in error && typeof (error as Record<string, unknown>).message === 'string'
+    )
+}
+
+const toErrorWithMessage = (maybeError: unknown): ErrorWithMessage => {
+    if (isErrorWithMessage(maybeError)) return maybeError
+
+    try {
+        return new Error(JSON.stringify(maybeError))
+    } catch {
+        // fallback in case there's an error stringifying the maybeError
+        // like with circular references for example.
+        return new Error(String(maybeError))
+    }
+}
+
+export const getErrorMessage = (error: unknown) => {
+    return toErrorWithMessage(error).message
+}