fix: recognize dynamic AI Tool nodes in validator (Issue #522 ) (#526 )

When n8n connects any node to an AI Agent's tool slot, it creates a dynamic Tool variant at runtime (e.g., googleDrive → googleDriveTool). These don't exist in npm packages, causing false "unknown node type" errors. Added validation-time inference: when a *Tool node type is not found, check if the base node exists. If yes, treat as valid with warning. Changes: - workflow-validator.ts: Add INFERRED_TOOL_VARIANT logic - node-similarity-service.ts: Add 98% confidence for valid Tool variants - Added 7 unit tests for inferred tool variant functionality Fixes #522 Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Romuald Członkowski <romualdczlonkowski@MacBook-Pro-Romuald.local> Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
fix: deprecate USE_FIXED_HTTP for SSE streaming support (Issue #524 ) (#525 )
2026-01-30 14:32:04 +00:00 · 2026-01-07 18:09:55 +01:00 · 2026-01-07 13:42:16 +01:00
22 changed files with 501 additions and 6845 deletions
--- a/.env.example
+++ b/.env.example
@@ -37,9 +37,11 @@ MCP_SERVER_HOST=localhost
 # Server mode: stdio (local) or http (remote)
 MCP_MODE=stdio

-# Use fixed HTTP implementation (recommended for stability)
-# Set to true to bypass StreamableHTTPServerTransport issues
-USE_FIXED_HTTP=true
+# DEPRECATED: USE_FIXED_HTTP is deprecated as of v2.31.8
+# The fixed HTTP implementation does not support SSE streaming required by
+# clients like OpenAI Codex. Use the default SingleSessionHTTPServer instead.
+# See: https://github.com/czlonkowski/n8n-mcp/issues/524
+# USE_FIXED_HTTP=true  # DO NOT USE - deprecated

 # HTTP Server Configuration (only used when MCP_MODE=http)
 PORT=3000
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
--- a/Dockerfile.railway
+++ b/Dockerfile.railway
@@ -74,7 +74,8 @@ ENV AUTH_TOKEN="REPLACE_THIS_AUTH_TOKEN_32_CHARS_MIN_abcdefgh"
 ENV NODE_ENV=production
 ENV IS_DOCKER=true
 ENV MCP_MODE=http
-ENV USE_FIXED_HTTP=true
+# NOTE: USE_FIXED_HTTP is deprecated. SingleSessionHTTPServer is now the default.
+# See: https://github.com/czlonkowski/n8n-mcp/issues/524
 ENV LOG_LEVEL=info
 ENV TRUST_PROXY=1
 ENV HOST=0.0.0.0
--- a/dist/services/node-similarity-service.d.ts.map
+++ b/dist/services/node-similarity-service.d.ts.map
@@ -1 +1 @@
-{"version":3,"file":"node-similarity-service.d.ts","sourceRoot":"","sources":["../../src/services/node-similarity-service.ts"],"names":[],"mappings":"AAAA,OAAO,EAAE,cAAc,EAAE,MAAM,6BAA6B,CAAC;AAG7D,MAAM,WAAW,cAAc;IAC7B,QAAQ,EAAE,MAAM,CAAC;IACjB,WAAW,EAAE,MAAM,CAAC;IACpB,UAAU,EAAE,MAAM,CAAC;IACnB,MAAM,EAAE,MAAM,CAAC;IACf,QAAQ,CAAC,EAAE,MAAM,CAAC;IAClB,WAAW,CAAC,EAAE,MAAM,CAAC;CACtB;AAED,MAAM,WAAW,eAAe;IAC9B,cAAc,EAAE,MAAM,CAAC;IACvB,aAAa,EAAE,MAAM,CAAC;IACtB,YAAY,EAAE,MAAM,CAAC;IACrB,YAAY,EAAE,MAAM,CAAC;IACrB,UAAU,EAAE,MAAM,CAAC;CACpB;AAED,MAAM,WAAW,oBAAoB;IACnC,OAAO,EAAE,MAAM,CAAC;IAChB,UAAU,EAAE,MAAM,CAAC;IACnB,UAAU,EAAE,MAAM,CAAC;IACnB,MAAM,EAAE,MAAM,CAAC;CAChB;AAED,qBAAa,qBAAqB;IAEhC,OAAO,CAAC,MAAM,CAAC,QAAQ,CAAC,iBAAiB,CAAM;IAC/C,OAAO,CAAC,MAAM,CAAC,QAAQ,CAAC,kBAAkB,CAAK;IAC/C,OAAO,CAAC,MAAM,CAAC,QAAQ,CAAC,mBAAmB,CAAK;IAChD,OAAO,CAAC,MAAM,CAAC,QAAQ,CAAC,iBAAiB,CAAiB;IAC1D,OAAO,CAAC,MAAM,CAAC,QAAQ,CAAC,mBAAmB,CAAO;IAElD,OAAO,CAAC,UAAU,CAAiB;IACnC,OAAO,CAAC,cAAc,CAAsC;IAC5D,OAAO,CAAC,SAAS,CAAsB;IACvC,OAAO,CAAC,WAAW,CAAa;IAChC,OAAO,CAAC,YAAY,CAAa;gBAErB,UAAU,EAAE,cAAc;IAStC,OAAO,CAAC,wBAAwB;IAkDhC,OAAO,CAAC,yBAAyB;IAuB3B,gBAAgB,CAAC,WAAW,EAAE,MAAM,EAAE,KAAK,GAAE,MAAU,GAAG,OAAO,CAAC,cAAc,EAAE,CAAC;IA8CzF,OAAO,CAAC,mBAAmB;IA0E3B,OAAO,CAAC,wBAAwB;IAuEhC,OAAO,CAAC,gBAAgB;IA2BxB,OAAO,CAAC,iBAAiB;IAUzB,OAAO,CAAC,mBAAmB;IAgB3B,OAAO,CAAC,eAAe;YAgDT,cAAc;IAqCrB,eAAe,IAAI,IAAI;IAUjB,YAAY,IAAI,OAAO,CAAC,IAAI,CAAC;IAQ1C,uBAAuB,CAAC,WAAW,EAAE,cAAc,EAAE,EAAE,WAAW,EAAE,MAAM,GAAG,MAAM;IA8BnF,aAAa,CAAC,UAAU,EAAE,cAAc,GAAG,OAAO;IAQlD,UAAU,IAAI,IAAI;CAGnB"}
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--- a/dist/services/node-similarity-service.js
+++ b/dist/services/node-similarity-service.js
@@ -2,6 +2,7 @@
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.NodeSimilarityService = void 0;
 const logger_1 = require("../utils/logger");
+const tool_variant_generator_1 = require("./tool-variant-generator");
 class NodeSimilarityService {
    constructor(repository) {
        this.nodeCache = null;
@@ -67,6 +68,22 @@ class NodeSimilarityService {
        if (!invalidType || invalidType.trim() === '') {
            return [];
        }
+        if (tool_variant_generator_1.ToolVariantGenerator.isToolVariantNodeType(invalidType)) {
+            const baseNodeType = tool_variant_generator_1.ToolVariantGenerator.getBaseNodeType(invalidType);
+            if (baseNodeType) {
+                const baseNode = this.repository.getNode(baseNodeType);
+                if (baseNode) {
+                    return [{
+                            nodeType: invalidType,
+                            displayName: `${baseNode.displayName} Tool`,
+                            confidence: 0.98,
+                            reason: `Dynamic AI Tool variant of ${baseNode.displayName}`,
+                            category: baseNode.category,
+                            description: 'Runtime-generated Tool variant for AI Agent integration'
+                        }];
+                }
+            }
+        }
        const suggestions = [];
        const mistakeSuggestion = this.checkCommonMistakes(invalidType);
        if (mistakeSuggestion) {
--- a/dist/services/node-similarity-service.js.map
+++ b/dist/services/node-similarity-service.js.map
--- a/dist/services/workflow-validator.d.ts.map
+++ b/dist/services/workflow-validator.d.ts.map
@@ -1 +1 @@
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--- a/dist/services/workflow-validator.js
+++ b/dist/services/workflow-validator.js
@@ -236,7 +236,31 @@ class WorkflowValidator {
                    }
                }
                const normalizedType = node_type_normalizer_1.NodeTypeNormalizer.normalizeToFullForm(node.type);
-                const nodeInfo = this.nodeRepository.getNode(normalizedType);
+                let nodeInfo = this.nodeRepository.getNode(normalizedType);
+                if (!nodeInfo && tool_variant_generator_1.ToolVariantGenerator.isToolVariantNodeType(normalizedType)) {
+                    const baseNodeType = tool_variant_generator_1.ToolVariantGenerator.getBaseNodeType(normalizedType);
+                    if (baseNodeType) {
+                        const baseNodeInfo = this.nodeRepository.getNode(baseNodeType);
+                        if (baseNodeInfo) {
+                            result.warnings.push({
+                                type: 'warning',
+                                nodeId: node.id,
+                                nodeName: node.name,
+                                message: `Node type "${node.type}" is inferred as a dynamic AI Tool variant of "${baseNodeType}". ` +
+                                    `This Tool variant is created by n8n at runtime when connecting "${baseNodeInfo.displayName}" to an AI Agent.`,
+                                code: 'INFERRED_TOOL_VARIANT'
+                            });
+                            nodeInfo = {
+                                ...baseNodeInfo,
+                                nodeType: normalizedType,
+                                displayName: `${baseNodeInfo.displayName} Tool`,
+                                isToolVariant: true,
+                                toolVariantOf: baseNodeType,
+                                isInferred: true
+                            };
+                        }
+                    }
+                }
                if (!nodeInfo) {
                    const suggestions = await this.similarityService.findSimilarNodes(node.type, 3);
                    let message = `Unknown node type: "${node.type}".`;
@@ -310,6 +334,9 @@ class WorkflowValidator {
                if (normalizedType.startsWith('nodes-langchain.')) {
                    continue;
                }
+                if (nodeInfo.isInferred) {
+                    continue;
+                }
                const paramsWithVersion = {
                    '@version': node.typeVersion || 1,
                    ...node.parameters
--- a/dist/services/workflow-validator.js.map
+++ b/dist/services/workflow-validator.js.map
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -12,7 +12,8 @@ services:
    environment:
      # Mode configuration
      MCP_MODE: ${MCP_MODE:-http}
-      USE_FIXED_HTTP: ${USE_FIXED_HTTP:-true}  # Use fixed implementation for stability
+      # NOTE: USE_FIXED_HTTP is deprecated. SingleSessionHTTPServer is now the default.
+      # See: https://github.com/czlonkowski/n8n-mcp/issues/524
      AUTH_TOKEN: ${AUTH_TOKEN:?AUTH_TOKEN is required for HTTP mode}
      
      # Application settings
--- a/docs/DOCKER_README.md
+++ b/docs/DOCKER_README.md
@@ -21,7 +21,6 @@ cd n8n-mcp
 # Create .env file with auth token
 cat > .env << EOF
 AUTH_TOKEN=$(openssl rand -base64 32)
-USE_FIXED_HTTP=true
 EOF

 # Start the server
@@ -46,7 +45,6 @@ docker pull ghcr.io/czlonkowski/n8n-mcp:latest
 docker run -d \
  --name n8n-mcp \
  -e MCP_MODE=http \
-  -e USE_FIXED_HTTP=true \
  -e AUTH_TOKEN=your-secure-token \
  -p 3000:3000 \
  ghcr.io/czlonkowski/n8n-mcp:latest
--- a/docs/HTTP_DEPLOYMENT.md
+++ b/docs/HTTP_DEPLOYMENT.md
@@ -67,7 +67,6 @@ Claude Desktop → mcp-remote → https://your-server.com
 # 1. Create environment file
 cat > .env << EOF
 AUTH_TOKEN=$(openssl rand -base64 32)
-USE_FIXED_HTTP=true
 MCP_MODE=http
 PORT=3000
 # Optional: Enable n8n management tools
@@ -106,7 +105,6 @@ npm run rebuild

 # 2. Configure environment
 export MCP_MODE=http
-export USE_FIXED_HTTP=true  # Important: Use fixed implementation
 export AUTH_TOKEN=$(openssl rand -base64 32)
 export PORT=3000

@@ -144,7 +142,6 @@ Skip HTTP entirely and use stdio mode directly:
 | Variable | Description | Example |
 |----------|-------------|------|
 | `MCP_MODE` | Must be set to `http` | `http` |
-| `USE_FIXED_HTTP` | **Important**: Set to `true` for stable implementation | `true` |
 | `AUTH_TOKEN` or `AUTH_TOKEN_FILE` | Authentication method | See security section |

 ### Optional Settings
@@ -417,7 +414,6 @@ services:
    environment:
      # Core configuration
      MCP_MODE: http
-      USE_FIXED_HTTP: true
      NODE_ENV: production
      
      # Security - Using file-based secret
@@ -500,7 +496,6 @@ WorkingDirectory=/opt/n8n-mcp
 # Use file-based secret
 Environment="AUTH_TOKEN_FILE=/etc/n8n-mcp/auth_token"
 Environment="MCP_MODE=http"
-Environment="USE_FIXED_HTTP=true"
 Environment="NODE_ENV=production"
 Environment="TRUST_PROXY=1"
 Environment="BASE_URL=https://n8n-mcp.example.com"
@@ -772,8 +767,8 @@ sudo ufw status  # Linux
 ```

 **"Stream is not readable":**
- Ensure `USE_FIXED_HTTP=true` is set
- Fixed in v2.3.2+
+- This issue was fixed in v2.3.2+ with the SingleSessionHTTPServer
+- No additional configuration needed

 **Bridge script not working:**
 ```bash
--- a/docs/INSTALLATION.md
+++ b/docs/INSTALLATION.md
@@ -18,7 +18,6 @@ The fastest way to get n8n-MCP running:
 # Using Docker (recommended)
 cat > .env << EOF
 AUTH_TOKEN=$(openssl rand -base64 32)
-USE_FIXED_HTTP=true
 EOF
 docker compose up -d
 ```
@@ -49,7 +48,6 @@ docker compose up -d
       
       environment:
         MCP_MODE: ${MCP_MODE:-http}
-         USE_FIXED_HTTP: ${USE_FIXED_HTTP:-true}
         AUTH_TOKEN: ${AUTH_TOKEN:?AUTH_TOKEN is required}
         NODE_ENV: ${NODE_ENV:-production}
         LOG_LEVEL: ${LOG_LEVEL:-info}
--- a/docs/RAILWAY_DEPLOYMENT.md
+++ b/docs/RAILWAY_DEPLOYMENT.md
@@ -98,7 +98,6 @@ These are automatically set by the Railway template:
 |----------|--------------|-------------|
 | `AUTH_TOKEN` | `REPLACE_THIS...` | **⚠️ CHANGE IMMEDIATELY** |
 | `MCP_MODE` | `http` | Required for cloud deployment |
-| `USE_FIXED_HTTP` | `true` | Stable HTTP implementation |
 | `NODE_ENV` | `production` | Production optimizations |
 | `LOG_LEVEL` | `info` | Balanced logging |
 | `TRUST_PROXY` | `1` | Railway runs behind proxy |
--- a/docs/README.md
+++ b/docs/README.md
@@ -40,7 +40,6 @@ Key configuration options:
 | Variable | Description | Default |
 |----------|-------------|---------|
 | `MCP_MODE` | Server mode: `stdio` or `http` | `stdio` |
-| `USE_FIXED_HTTP` | Use fixed HTTP implementation (v2.3.2+) | `true` |
 | `AUTH_TOKEN` | Authentication token for HTTP mode | Required |
 | `PORT` | HTTP server port | `3000` |
 | `LOG_LEVEL` | Logging verbosity | `info` |
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
  "name": "n8n-mcp",
-  "version": "2.31.7",
+  "version": "2.31.9",
  "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
  "main": "dist/index.js",
  "types": "dist/index.d.ts",
@@ -22,9 +22,9 @@
    "test-nodes": "node dist/scripts/test-nodes.js",
    "start": "node dist/mcp/index.js",
    "start:http": "MCP_MODE=http node dist/mcp/index.js",
-    "start:http:fixed": "MCP_MODE=http USE_FIXED_HTTP=true node dist/mcp/index.js",
+    "start:http:fixed:deprecated": "echo 'DEPRECATED: USE_FIXED_HTTP is deprecated. Use npm run start:http instead.' && MCP_MODE=http USE_FIXED_HTTP=true node dist/mcp/index.js",
    "start:n8n": "N8N_MODE=true MCP_MODE=http node dist/mcp/index.js",
-    "http": "npm run build && npm run start:http:fixed",
+    "http": "npm run build && npm run start:http",
    "dev": "npm run build && npm run rebuild && npm run validate",
    "dev:http": "MCP_MODE=http nodemon --watch src --ext ts --exec 'npm run build && npm run start:http'",
    "test:single-session": "./scripts/test-single-session.sh",
--- a/scripts/test-url-configuration.ts
+++ b/scripts/test-url-configuration.ts
@@ -71,10 +71,12 @@ const testCases: TestCase[] = [
    }
  },
  {
-    name: 'Fixed HTTP implementation',
+    // DEPRECATED: This test case tests the deprecated fixed HTTP implementation
+    // See: https://github.com/czlonkowski/n8n-mcp/issues/524
+    name: 'Fixed HTTP implementation (DEPRECATED)',
    env: {
      MCP_MODE: 'http',
-      USE_FIXED_HTTP: 'true',
+      USE_FIXED_HTTP: 'true',  // DEPRECATED: Will be removed in future version
      AUTH_TOKEN: 'test-token-for-testing-only',
      PORT: '3005',
      BASE_URL: 'https://fixed.example.com'
--- a/src/http-server.ts
+++ b/src/http-server.ts
@@ -1,7 +1,14 @@
 #!/usr/bin/env node
 /**
- * Fixed HTTP server for n8n-MCP that properly handles StreamableHTTPServerTransport initialization
- * This implementation ensures the transport is properly initialized before handling requests
+ * @deprecated This fixed HTTP server is deprecated as of v2.31.8.
+ * Use SingleSessionHTTPServer from http-server-single-session.ts instead.
+ *
+ * This implementation does not support SSE streaming required by clients like OpenAI Codex.
+ * See: https://github.com/czlonkowski/n8n-mcp/issues/524
+ *
+ * Original purpose: Fixed HTTP server for n8n-MCP that properly handles
+ * StreamableHTTPServerTransport initialization by bypassing it entirely.
+ * This implementation ensures the transport is properly initialized before handling requests.
 */
 import express from 'express';
 import { Server } from '@modelcontextprotocol/sdk/server/index.js';
@@ -125,7 +132,18 @@ async function shutdown() {
  }
 }

+/**
+ * @deprecated Use SingleSessionHTTPServer from http-server-single-session.ts instead.
+ * This function does not support SSE streaming required by clients like OpenAI Codex.
+ */
 export async function startFixedHTTPServer() {
+  // Log deprecation warning
+  logger.warn(
+    'DEPRECATION: startFixedHTTPServer() is deprecated as of v2.31.8. ' +
+    'Use SingleSessionHTTPServer which supports SSE streaming. ' +
+    'See: https://github.com/czlonkowski/n8n-mcp/issues/524'
+  );
+
  validateEnvironment();
  
  const app = express();
--- a/src/mcp/index.ts
+++ b/src/mcp/index.ts
@@ -124,9 +124,23 @@ Learn more: https://github.com/czlonkowski/n8n-mcp/blob/main/PRIVACY.md
    checkpoints.push(STARTUP_CHECKPOINTS.MCP_HANDSHAKE_STARTING);
    
    if (mode === 'http') {
-      // Check if we should use the fixed implementation
+      // Check if we should use the fixed implementation (DEPRECATED)
      if (process.env.USE_FIXED_HTTP === 'true') {
-        // Use the fixed HTTP implementation that bypasses StreamableHTTPServerTransport issues
+        // DEPRECATION WARNING: Fixed HTTP implementation is deprecated
+        // It does not support SSE streaming required by clients like OpenAI Codex
+        logger.warn(
+          'DEPRECATION WARNING: USE_FIXED_HTTP=true is deprecated as of v2.31.8. ' +
+          'The fixed HTTP implementation does not support SSE streaming required by clients like OpenAI Codex. ' +
+          'Please unset USE_FIXED_HTTP to use the modern SingleSessionHTTPServer which supports both JSON-RPC and SSE. ' +
+          'This option will be removed in a future version. See: https://github.com/czlonkowski/n8n-mcp/issues/524'
+        );
+        console.warn('\n⚠️  DEPRECATION WARNING ⚠️');
+        console.warn('USE_FIXED_HTTP=true is deprecated as of v2.31.8.');
+        console.warn('The fixed HTTP implementation does not support SSE streaming.');
+        console.warn('Please unset USE_FIXED_HTTP to use SingleSessionHTTPServer.');
+        console.warn('See: https://github.com/czlonkowski/n8n-mcp/issues/524\n');
+
+        // Use the deprecated fixed HTTP implementation
        const { startFixedHTTPServer } = await import('../http-server');
        await startFixedHTTPServer();
      } else {
--- a/src/services/node-similarity-service.ts
+++ b/src/services/node-similarity-service.ts
@@ -1,5 +1,6 @@
 import { NodeRepository } from '../database/node-repository';
 import { logger } from '../utils/logger';
+import { ToolVariantGenerator } from './tool-variant-generator';

 export interface NodeSuggestion {
  nodeType: string;
@@ -126,6 +127,25 @@ export class NodeSimilarityService {
      return [];
    }

+    // Check if this is a Tool variant and base node exists (Issue #522)
+    // Dynamic AI Tool variants like googleDriveTool are created at runtime by n8n
+    if (ToolVariantGenerator.isToolVariantNodeType(invalidType)) {
+      const baseNodeType = ToolVariantGenerator.getBaseNodeType(invalidType);
+      if (baseNodeType) {
+        const baseNode = this.repository.getNode(baseNodeType);
+        if (baseNode) {
+          return [{
+            nodeType: invalidType,
+            displayName: `${baseNode.displayName} Tool`,
+            confidence: 0.98,
+            reason: `Dynamic AI Tool variant of ${baseNode.displayName}`,
+            category: baseNode.category,
+            description: 'Runtime-generated Tool variant for AI Agent integration'
+          }];
+        }
+      }
+    }
+
    const suggestions: NodeSuggestion[] = [];

    // First, check for exact common mistakes
--- a/src/services/workflow-validator.ts
+++ b/src/services/workflow-validator.ts
@@ -398,7 +398,39 @@ export class WorkflowValidator {
        const normalizedType = NodeTypeNormalizer.normalizeToFullForm(node.type);

        // Get node definition using normalized type (needed for typeVersion validation)
-        const nodeInfo = this.nodeRepository.getNode(normalizedType);
+        let nodeInfo = this.nodeRepository.getNode(normalizedType);
+
+        // Check if this is a dynamic Tool variant (e.g., googleDriveTool, googleSheetsTool)
+        // n8n creates these at runtime when ANY node is used in an AI Agent's tool slot,
+        // but they don't exist in npm packages. We infer validity if the base node exists.
+        // See: https://github.com/czlonkowski/n8n-mcp/issues/522
+        if (!nodeInfo && ToolVariantGenerator.isToolVariantNodeType(normalizedType)) {
+          const baseNodeType = ToolVariantGenerator.getBaseNodeType(normalizedType);
+          if (baseNodeType) {
+            const baseNodeInfo = this.nodeRepository.getNode(baseNodeType);
+            if (baseNodeInfo) {
+              // Valid inferred tool variant - base node exists
+              result.warnings.push({
+                type: 'warning',
+                nodeId: node.id,
+                nodeName: node.name,
+                message: `Node type "${node.type}" is inferred as a dynamic AI Tool variant of "${baseNodeType}". ` +
+                  `This Tool variant is created by n8n at runtime when connecting "${baseNodeInfo.displayName}" to an AI Agent.`,
+                code: 'INFERRED_TOOL_VARIANT'
+              });
+
+              // Create synthetic nodeInfo for validation continuity
+              nodeInfo = {
+                ...baseNodeInfo,
+                nodeType: normalizedType,
+                displayName: `${baseNodeInfo.displayName} Tool`,
+                isToolVariant: true,
+                toolVariantOf: baseNodeType,
+                isInferred: true
+              };
+            }
+          }
+        }

        if (!nodeInfo) {

@@ -494,6 +526,13 @@ export class WorkflowValidator {
          continue;
        }

+        // Skip PARAMETER validation for inferred tool variants (Issue #522)
+        // They have a different property structure (toolDescription added at runtime)
+        // that doesn't match the base node's schema. TypeVersion validation above still runs.
+        if ((nodeInfo as any).isInferred) {
+          continue;
+        }
+
        // Validate node configuration
        // Add @version to parameters for displayOptions evaluation (supports _cnd operators)
        const paramsWithVersion = {
--- a/tests/unit/services/workflow-validator-tool-variants.test.ts
+++ b/tests/unit/services/workflow-validator-tool-variants.test.ts
@@ -599,4 +599,294 @@ describe('WorkflowValidator - Tool Variant Validation', () => {
      expect(invalidToolErrors.length).toBeGreaterThan(0);
    });
  });
+
+  describe('validateAllNodes - Inferred Tool Variants (Issue #522)', () => {
+    /**
+     * Tests for dynamic AI Tool nodes that are created at runtime by n8n
+     * when ANY node is used in an AI Agent's tool slot.
+     *
+     * These nodes (e.g., googleDriveTool, googleSheetsTool) don't exist in npm packages
+     * but are valid when the base node exists.
+     */
+
+    beforeEach(() => {
+      // Update mock repository to include Google nodes
+      mockRepository.getNode = vi.fn((nodeType: string) => {
+        // Base node with Tool variant
+        if (nodeType === 'nodes-base.supabase') {
+          return {
+            nodeType: 'nodes-base.supabase',
+            displayName: 'Supabase',
+            isAITool: true,
+            hasToolVariant: true,
+            isToolVariant: false,
+            isTrigger: false,
+            properties: []
+          };
+        }
+
+        // Tool variant in database
+        if (nodeType === 'nodes-base.supabaseTool') {
+          return {
+            nodeType: 'nodes-base.supabaseTool',
+            displayName: 'Supabase Tool',
+            isAITool: true,
+            hasToolVariant: false,
+            isToolVariant: true,
+            toolVariantOf: 'nodes-base.supabase',
+            isTrigger: false,
+            properties: []
+          };
+        }
+
+        // Google Drive base node (exists, but no Tool variant in DB)
+        if (nodeType === 'nodes-base.googleDrive') {
+          return {
+            nodeType: 'nodes-base.googleDrive',
+            displayName: 'Google Drive',
+            isAITool: false, // Not marked as AI tool in npm package
+            hasToolVariant: false, // No Tool variant in database
+            isToolVariant: false,
+            isTrigger: false,
+            properties: [],
+            category: 'files'
+          };
+        }
+
+        // Google Sheets base node (exists, but no Tool variant in DB)
+        if (nodeType === 'nodes-base.googleSheets') {
+          return {
+            nodeType: 'nodes-base.googleSheets',
+            displayName: 'Google Sheets',
+            isAITool: false,
+            hasToolVariant: false,
+            isToolVariant: false,
+            isTrigger: false,
+            properties: [],
+            category: 'productivity'
+          };
+        }
+
+        // AI Agent node
+        if (nodeType === 'nodes-langchain.agent') {
+          return {
+            nodeType: 'nodes-langchain.agent',
+            displayName: 'AI Agent',
+            isAITool: false,
+            hasToolVariant: false,
+            isToolVariant: false,
+            isTrigger: false,
+            properties: []
+          };
+        }
+
+        return null; // Unknown node
+      }) as any;
+    });
+
+    it('should pass validation for googleDriveTool when googleDrive exists', async () => {
+      const workflow = {
+        nodes: [
+          {
+            id: 'drive-tool-1',
+            name: 'Google Drive Tool',
+            type: 'n8n-nodes-base.googleDriveTool',
+            typeVersion: 3,
+            position: [250, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const result = await validator.validateWorkflow(workflow);
+
+      // Should NOT have "Unknown node type" error
+      const unknownErrors = result.errors.filter(e =>
+        e.message && e.message.includes('Unknown node type')
+      );
+      expect(unknownErrors).toHaveLength(0);
+
+      // Should have INFERRED_TOOL_VARIANT warning
+      const inferredWarnings = result.warnings.filter(e =>
+        (e as any).code === 'INFERRED_TOOL_VARIANT'
+      );
+      expect(inferredWarnings).toHaveLength(1);
+      expect(inferredWarnings[0].message).toContain('googleDriveTool');
+      expect(inferredWarnings[0].message).toContain('Google Drive');
+    });
+
+    it('should pass validation for googleSheetsTool when googleSheets exists', async () => {
+      const workflow = {
+        nodes: [
+          {
+            id: 'sheets-tool-1',
+            name: 'Google Sheets Tool',
+            type: 'n8n-nodes-base.googleSheetsTool',
+            typeVersion: 4,
+            position: [250, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const result = await validator.validateWorkflow(workflow);
+
+      // Should NOT have "Unknown node type" error
+      const unknownErrors = result.errors.filter(e =>
+        e.message && e.message.includes('Unknown node type')
+      );
+      expect(unknownErrors).toHaveLength(0);
+
+      // Should have INFERRED_TOOL_VARIANT warning
+      const inferredWarnings = result.warnings.filter(e =>
+        (e as any).code === 'INFERRED_TOOL_VARIANT'
+      );
+      expect(inferredWarnings).toHaveLength(1);
+      expect(inferredWarnings[0].message).toContain('googleSheetsTool');
+      expect(inferredWarnings[0].message).toContain('Google Sheets');
+    });
+
+    it('should report error for unknownNodeTool when base node does not exist', async () => {
+      const workflow = {
+        nodes: [
+          {
+            id: 'unknown-tool-1',
+            name: 'Unknown Tool',
+            type: 'n8n-nodes-base.nonExistentNodeTool',
+            typeVersion: 1,
+            position: [250, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const result = await validator.validateWorkflow(workflow);
+
+      // Should have "Unknown node type" error
+      const unknownErrors = result.errors.filter(e =>
+        e.message && e.message.includes('Unknown node type')
+      );
+      expect(unknownErrors).toHaveLength(1);
+
+      // Should NOT have INFERRED_TOOL_VARIANT warning
+      const inferredWarnings = result.warnings.filter(e =>
+        (e as any).code === 'INFERRED_TOOL_VARIANT'
+      );
+      expect(inferredWarnings).toHaveLength(0);
+    });
+
+    it('should handle multiple inferred tool variants in same workflow', async () => {
+      const workflow = {
+        nodes: [
+          {
+            id: 'drive-tool-1',
+            name: 'Google Drive Tool',
+            type: 'n8n-nodes-base.googleDriveTool',
+            typeVersion: 3,
+            position: [250, 300] as [number, number],
+            parameters: {}
+          },
+          {
+            id: 'sheets-tool-1',
+            name: 'Google Sheets Tool',
+            type: 'n8n-nodes-base.googleSheetsTool',
+            typeVersion: 4,
+            position: [250, 400] as [number, number],
+            parameters: {}
+          },
+          {
+            id: 'agent-1',
+            name: 'AI Agent',
+            type: '@n8n/n8n-nodes-langchain.agent',
+            typeVersion: 1.7,
+            position: [450, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {
+          'Google Drive Tool': {
+            ai_tool: [[{ node: 'AI Agent', type: 'ai_tool', index: 0 }]]
+          },
+          'Google Sheets Tool': {
+            ai_tool: [[{ node: 'AI Agent', type: 'ai_tool', index: 0 }]]
+          }
+        }
+      };
+
+      const result = await validator.validateWorkflow(workflow);
+
+      // Should NOT have "Unknown node type" errors
+      const unknownErrors = result.errors.filter(e =>
+        e.message && e.message.includes('Unknown node type')
+      );
+      expect(unknownErrors).toHaveLength(0);
+
+      // Should have 2 INFERRED_TOOL_VARIANT warnings
+      const inferredWarnings = result.warnings.filter(e =>
+        (e as any).code === 'INFERRED_TOOL_VARIANT'
+      );
+      expect(inferredWarnings).toHaveLength(2);
+    });
+
+    it('should prefer database record over inference for supabaseTool', async () => {
+      const workflow = {
+        nodes: [
+          {
+            id: 'supabase-tool-1',
+            name: 'Supabase Tool',
+            type: 'n8n-nodes-base.supabaseTool',
+            typeVersion: 1,
+            position: [250, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const result = await validator.validateWorkflow(workflow);
+
+      // Should NOT have "Unknown node type" error
+      const unknownErrors = result.errors.filter(e =>
+        e.message && e.message.includes('Unknown node type')
+      );
+      expect(unknownErrors).toHaveLength(0);
+
+      // Should NOT have INFERRED_TOOL_VARIANT warning (it's in database)
+      const inferredWarnings = result.warnings.filter(e =>
+        (e as any).code === 'INFERRED_TOOL_VARIANT'
+      );
+      expect(inferredWarnings).toHaveLength(0);
+    });
+
+    it('should include helpful message in warning', async () => {
+      const workflow = {
+        nodes: [
+          {
+            id: 'drive-tool-1',
+            name: 'Google Drive Tool',
+            type: 'n8n-nodes-base.googleDriveTool',
+            typeVersion: 3,
+            position: [250, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const result = await validator.validateWorkflow(workflow);
+
+      const inferredWarning = result.warnings.find(e =>
+        (e as any).code === 'INFERRED_TOOL_VARIANT'
+      );
+
+      expect(inferredWarning).toBeDefined();
+      expect(inferredWarning!.message).toContain('inferred as a dynamic AI Tool variant');
+      expect(inferredWarning!.message).toContain('nodes-base.googleDrive');
+      expect(inferredWarning!.message).toContain('Google Drive');
+      expect(inferredWarning!.message).toContain('AI Agent');
+    });
+  });
 });