diff --git a/app/api/execute/route.ts b/app/api/execute/route.ts
index 4b363eba37..e33593f52f 100644
--- a/app/api/execute/route.ts
+++ b/app/api/execute/route.ts
@@ -12,7 +12,7 @@ export async function POST(req: NextRequest) {
   try {
     const body = await req.json()
 
-    const { code, timeout = 3000 } = body
+    const { code, params = {}, timeout = 3000 } = body
 
     // Check if code contains unresolved template variables
     if (code.includes('<') && code.includes('>')) {
@@ -23,6 +23,7 @@ export async function POST(req: NextRequest) {
 
     // Create a secure context with console logging
     const context = createContext({
+      params,
       console: {
         log: (...args: any[]) => {
           const logMessage =
@@ -42,7 +43,6 @@ export async function POST(req: NextRequest) {
       },
     })
 
-    // Create and run the script
     const script = new Script(`
       (async () => {
         try {
diff --git a/executor/handlers.ts b/executor/handlers.ts
index 682380d8c3..76ed543592 100644
--- a/executor/handlers.ts
+++ b/executor/handlers.ts
@@ -69,6 +69,22 @@ export class AgentBlockHandler implements BlockHandler {
     const formattedTools = Array.isArray(inputs.tools)
       ? inputs.tools
           .map((tool: any) => {
+            // Handle custom tools
+            if (tool.type === 'custom-tool' && tool.schema) {
+              return {
+                id: `custom_${tool.title}`,
+                name: tool.schema.function.name,
+                description: tool.schema.function.description || '',
+                params: tool.params || {},
+                parameters: {
+                  type: tool.schema.function.parameters.type,
+                  properties: tool.schema.function.parameters.properties,
+                  required: tool.schema.function.parameters.required || [],
+                },
+              }
+            }
+
+            // Handle regular block tools
             const blockFound = getAllBlocks().find((b) => b.type === tool.type)
             const toolId = blockFound?.tools.access[0]
             if (!toolId) return null
diff --git a/providers/utils.ts b/providers/utils.ts
index b5b93f8cf0..de1f6b228a 100644
--- a/providers/utils.ts
+++ b/providers/utils.ts
@@ -1,9 +1,10 @@
+import { useCustomToolsStore } from '@/stores/custom-tools/store'
 import { anthropicProvider } from './anthropic'
 import { cerebrasProvider } from './cerebras'
 import { deepseekProvider } from './deepseek'
 import { googleProvider } from './google'
 import { openaiProvider } from './openai'
-import { ProviderConfig, ProviderId } from './types'
+import { ProviderConfig, ProviderId, ProviderToolConfig } from './types'
 import { xAIProvider } from './xai'
 
 /**
@@ -192,3 +193,37 @@ export function extractAndParseJSON(content: string): any {
     }
   }
 }
+
+/**
+ * Transforms a custom tool schema into a provider tool config
+ */
+export function transformCustomTool(customTool: any): ProviderToolConfig {
+  const schema = customTool.schema
+
+  if (!schema || !schema.function) {
+    throw new Error('Invalid custom tool schema')
+  }
+
+  return {
+    id: `custom_${customTool.id}`, // Prefix with 'custom_' to identify custom tools
+    name: schema.function.name,
+    description: schema.function.description || '',
+    params: {}, // This will be derived from parameters
+    parameters: {
+      type: schema.function.parameters.type,
+      properties: schema.function.parameters.properties,
+      required: schema.function.parameters.required || [],
+    },
+  }
+}
+
+/**
+ * Gets all available custom tools as provider tool configs
+ */
+export function getCustomTools(): ProviderToolConfig[] {
+  // Get custom tools from the store
+  const customTools = useCustomToolsStore.getState().getAllTools()
+
+  // Transform each custom tool into a provider tool config
+  return customTools.map(transformCustomTool)
+}
diff --git a/providers/xai/index.ts b/providers/xai/index.ts
index 466882a40b..f6cb603b7f 100644
--- a/providers/xai/index.ts
+++ b/providers/xai/index.ts
@@ -1,4 +1,5 @@
 import OpenAI from 'openai'
+import { executeTool } from '@/tools'
 import { ProviderConfig, ProviderRequest, ProviderResponse } from '../types'
 
 export const xAIProvider: ProviderConfig = {
@@ -141,13 +142,7 @@ export const xAIProvider: ProviderConfig = {
             const tool = request.tools?.find((t) => t.id === toolName)
             if (!tool) continue
 
-            const { executeTool } = await import('@/tools')
             const mergedArgs = { ...tool.params, ...toolArgs }
-            console.log(`Merged tool args for ${toolName}:`, {
-              toolParams: tool.params,
-              llmArgs: toolArgs,
-              mergedArgs,
-            })
             const result = await executeTool(toolName, mergedArgs, true)
 
             if (!result.success) continue
diff --git a/serializer/index.ts b/serializer/index.ts
index bd64aa7d04..120459112b 100644
--- a/serializer/index.ts
+++ b/serializer/index.ts
@@ -28,13 +28,36 @@ export class Serializer {
       throw new Error(`Invalid block type: ${block.type}`)
     }
 
-    // Get tool ID from block config
-    const toolId = blockConfig.tools.config?.tool
-      ? blockConfig.tools.config.tool(this.extractParams(block))
-      : blockConfig.tools.access[0]
-
-    // Extract params from subBlocks
+    // Check if this is an agent block with custom tools
     const params = this.extractParams(block)
+    let toolId = ''
+
+    if (block.type === 'agent' && params.tools) {
+      // Process the tools in the agent block
+      try {
+        const tools = Array.isArray(params.tools) ? params.tools : JSON.parse(params.tools)
+
+        // If there are custom tools, we just keep them as is
+        // They'll be handled by the executor during runtime
+
+        // For non-custom tools, we determine the tool ID
+        const nonCustomTools = tools.filter((tool: any) => tool.type !== 'custom-tool')
+        if (nonCustomTools.length > 0) {
+          toolId = blockConfig.tools.config?.tool
+            ? blockConfig.tools.config.tool(params)
+            : blockConfig.tools.access[0]
+        }
+      } catch (error) {
+        console.error('Error processing tools in agent block:', error)
+        // Default to the first tool if we can't process tools
+        toolId = blockConfig.tools.access[0]
+      }
+    } else {
+      // For non-agent blocks, get tool ID from block config as usual
+      toolId = blockConfig.tools.config?.tool
+        ? blockConfig.tools.config.tool(params)
+        : blockConfig.tools.access[0]
+    }
 
     // Get inputs from block config
     const inputs: Record<string, any> = {}
diff --git a/tools/index.ts b/tools/index.ts
index 9ba7efa707..2ab3b8197d 100644
--- a/tools/index.ts
+++ b/tools/index.ts
@@ -1,3 +1,4 @@
+import { useCustomToolsStore } from '@/stores/custom-tools/store'
 import { visionTool as crewAIVision } from './crewai/vision'
 import { scrapeTool } from './firecrawl/scrape'
 import { functionExecuteTool as functionExecute } from './function/execute'
@@ -67,7 +68,94 @@ export const tools: Record<string, ToolConfig> = {
 
 // Get a tool by its ID
 export function getTool(toolId: string): ToolConfig | undefined {
-  return tools[toolId]
+  // Check for built-in tools
+  const builtInTool = tools[toolId]
+  if (builtInTool) return builtInTool
+
+  // Check if it's a custom tool
+  if (toolId.startsWith('custom_')) {
+    return getCustomTool(toolId)
+  }
+
+  return undefined
+}
+
+// Create a tool config from a custom tool definition
+function getCustomTool(customToolId: string): ToolConfig | undefined {
+  // Extract the identifier part (could be UUID or title)
+  const identifier = customToolId.replace('custom_', '')
+
+  const customToolsStore = useCustomToolsStore.getState()
+
+  // Try to find the tool directly by ID first
+  let customTool = customToolsStore.getTool(identifier)
+
+  // If not found by ID, try to find by title (for backward compatibility)
+  if (!customTool) {
+    const allTools = customToolsStore.getAllTools()
+    customTool = allTools.find((tool) => tool.title === identifier)
+  }
+
+  if (!customTool) {
+    console.error(`Custom tool not found: ${identifier}`)
+    return undefined
+  }
+
+  // Create a parameter schema from the custom tool schema
+  const params: Record<string, any> = {}
+
+  if (customTool.schema.function?.parameters?.properties) {
+    Object.entries(customTool.schema.function.parameters.properties).forEach(([key, config]) => {
+      params[key] = {
+        type: config.type || 'string',
+        required: customTool.schema.function.parameters.required?.includes(key) || false,
+        requiredForToolCall: customTool.schema.function.parameters.required?.includes(key) || false,
+        description: config.description || '',
+      }
+    })
+  }
+
+  // Create a tool config for the custom tool
+  return {
+    id: customToolId,
+    name: customTool.title,
+    description: customTool.schema.function?.description || '',
+    version: '1.0.0',
+    params,
+
+    // Request configuration - for custom tools we'll use the execute endpoint
+    request: {
+      url: '/api/execute',
+      method: 'POST',
+      headers: () => ({ 'Content-Type': 'application/json' }),
+      body: (params: Record<string, any>) => {
+        // Include everything needed for execution
+        return {
+          code: customTool.code,
+          params: params, // These will be available in the VM context
+          schema: customTool.schema.function.parameters, // For validation on the client side
+        }
+      },
+      isInternalRoute: true,
+    },
+
+    // Response handling
+    transformResponse: async (response: Response) => {
+      const data = await response.json()
+
+      if (!data.success) {
+        throw new Error(data.error || 'Custom tool execution failed')
+      }
+
+      return {
+        success: true,
+        output: data.output.result || data.output,
+        error: undefined,
+      }
+    },
+    transformError: (error: any) =>
+      `Custom tool execution error: ${error.message || 'Unknown error'}`,
+  }
 }
 
 // Execute a tool by calling either the proxy for external APIs or directly for internal routes
@@ -78,10 +166,6 @@ export async function executeTool(
 ): Promise<ToolResponse> {
   try {
     const tool = getTool(toolId)
-    console.log(`Tool being called: ${toolId}`, {
-      params: { ...params, apiKey: params.apiKey ? '[REDACTED]' : undefined },
-      skipProxy,
-    })
 
     // Validate the tool and its parameters
     validateToolRequest(toolId, tool, params)
@@ -93,21 +177,25 @@ export async function executeTool(
 
     // For internal routes or when skipProxy is true, call the API directly
     if (tool.request.isInternalRoute || skipProxy) {
-      console.log(`Calling internal request for ${toolId}`)
       const result = await handleInternalRequest(toolId, tool, params)
-      console.log(`Tool ${toolId} execution result:`, {
-        success: result.success,
-        outputKeys: result.success ? Object.keys(result.output) : [],
-        error: result.error,
-      })
       return result
     }
 
     // For external APIs, use the proxy
-    console.log(`Calling proxy request for ${toolId}`)
     return await handleProxyRequest(toolId, params)
   } catch (error: any) {
     console.error(`Error executing tool ${toolId}:`, error)
+
+    // For custom tools, provide more helpful error information
+    if (toolId.startsWith('custom_')) {
+      const identifier = toolId.replace('custom_', '')
+      const allTools = useCustomToolsStore.getState().getAllTools()
+      const availableTools = allTools.map((t) => ({ id: t.id, title: t.title }))
+
+      console.error('Available custom tools:', availableTools)
+      console.error(`Looking for custom tool with identifier: ${identifier}`)
+    }
+
     return {
       success: false,
       output: {},
@@ -124,17 +212,113 @@ async function handleInternalRequest(
   tool: ToolConfig,
   params: Record<string, any>
 ): Promise<ToolResponse> {
-  // Log the request for debugging
-  console.log(`Executing tool ${toolId} with params:`, {
-    toolId,
-    params: { ...params, apiKey: params.apiKey ? '[REDACTED]' : undefined },
-  })
-
   // Format the request parameters
   const requestParams = formatRequestParams(tool, params)
 
-  // Execute the request
-  return await executeRequest(toolId, tool, requestParams)
+  try {
+    const baseUrl = process.env.NEXT_PUBLIC_APP_URL || ''
+    // Handle the case where url may be a function or string
+    const endpointUrl =
+      typeof tool.request.url === 'function' ? tool.request.url(params) : tool.request.url
+
+    const fullUrl = new URL(endpointUrl, baseUrl).toString()
+
+    // For custom tools, validate parameters on the client side before sending
+    if (toolId.startsWith('custom_') && tool.request.body) {
+      const requestBody = tool.request.body(params)
+      if (requestBody.schema && requestBody.params) {
+        validateClientSideParams(requestBody.params, requestBody.schema)
+      }
+    }
+
+    const response = await fetch(fullUrl, {
+      method: requestParams.method,
+      headers: requestParams.headers,
+      body: requestParams.body,
+    })
+
+    if (!response.ok) {
+      let errorData
+      try {
+        errorData = await response.json()
+      } catch (e) {
+        errorData = { error: response.statusText }
+      }
+
+      throw new Error(errorData.error || `Request failed with status ${response.status}`)
+    }
+
+    // Use the tool's response transformer if available
+    if (tool.transformResponse) {
+      return await tool.transformResponse(response)
+    }
+
+    // Default response handling
+    const data = await response.json()
+    return {
+      success: true,
+      output: data.output || data,
+      error: undefined,
+    }
+  } catch (error: any) {
+    // Use the tool's error transformer if available
+    if (tool.transformError) {
+      return {
+        success: false,
+        output: {},
+        error: tool.transformError(error),
+      }
+    }
+
+    return {
+      success: false,
+      output: {},
+      error: error.message || 'Request failed',
+    }
+  }
+}
+
+/**
+ * Validates parameters on the client side before sending to the execute endpoint
+ */
+function validateClientSideParams(
+  params: Record<string, any>,
+  schema: { type: string; properties: Record<string, any>; required?: string[] }
+) {
+  if (!schema || schema.type !== 'object') {
+    throw new Error('Invalid schema format')
+  }
+
+  // Check required parameters
+  if (schema.required) {
+    for (const requiredParam of schema.required) {
+      if (!(requiredParam in params)) {
+        throw new Error(`Required parameter missing: ${requiredParam}`)
+      }
+    }
+  }
+
+  // Check parameter types (basic validation)
+  for (const [paramName, paramValue] of Object.entries(params)) {
+    const paramSchema = schema.properties[paramName]
+    if (!paramSchema) {
+      throw new Error(`Unknown parameter: ${paramName}`)
+    }
+
+    // Basic type checking
+    const type = paramSchema.type
+    if (type === 'string' && typeof paramValue !== 'string') {
+      throw new Error(`Parameter ${paramName} should be a string`)
+    } else if (type === 'number' && typeof paramValue !== 'number') {
+      throw new Error(`Parameter ${paramName} should be a number`)
+    } else if (type === 'boolean' && typeof paramValue !== 'boolean') {
+      throw new Error(`Parameter ${paramName} should be a boolean`)
+    } else if (type === 'array' && !Array.isArray(paramValue)) {
+      throw new Error(`Parameter ${paramName} should be an array`)
+    } else if (type === 'object' && (typeof paramValue !== 'object' || paramValue === null)) {
+      throw new Error(`Parameter ${paramName} should be an object`)
+    }
+  }
 }
 
 /**
diff --git a/tools/utils.ts b/tools/utils.ts
index 325696ae4e..209402b473 100644
--- a/tools/utils.ts
+++ b/tools/utils.ts
@@ -66,14 +66,8 @@ export async function executeRequest(
   try {
     const { url, method, headers, body } = requestParams
 
-    // Log the request for debugging
-    console.log(`Executing tool ${toolId}:`, { url, method })
-
     const externalResponse = await fetch(url, { method, headers, body })
 
-    // Log response status
-    console.log(`${toolId} response status:`, externalResponse.status, externalResponse.statusText)
-
     if (!externalResponse.ok) {
       let errorContent
       try {