docs(tools): add Quick Selection Guide and common scenarios

Adds decision tree and real-world examples to existing Tools taxonomy:
- ASCII decision tree for quick tool type selection
- 6 common use cases with specific recommendations
- Integrates with existing Native/Workspace/MCP/OpenAPI explanations

Addresses user confusion about when to use each tool type.
Verified against existing UI paths and security warnings.

AI-assisted drafting; manually reviewed and validated.

Signed-off-by: Hera and Hades
Signed-off-by: HeraAndHades <christian93neumann@gmail.com>

Author: HeraAndHades

docs/features/extensibility/plugin/tools/index.mdx

@@ -47,7 +47,77 @@ These are **Python scripts** that run directly within the Open WebUI environment
 - **MCPO (Proxy)**: Most community MCP servers use `stdio` (local command line). To use these in Open WebUI, you use the [**MCPO Proxy**](../../plugin/tools/openapi-servers/mcp.mdx) to bridge the connection.
 
 ### 4. OpenAPI / Function Calling Servers
-Generic web servers that provide an OpenAPI (`.json` or `.yaml`) specification. Open WebUI can ingest these specs and treat every endpoint as a tool.
+Generic web servers that provide an OpenAPI (`.json` or `.yaml`) specification.
+Open WebUI can ingest these specs and treat every endpoint as a tool.
+
+---
+
+## Quick Selection Guide
+
+🎯 Not sure which tool type to use?
+Follow this decision tree.
+
+### Decision Tree
+
+```
+Do you need to add new AI capabilities (web search, image gen, etc.)?
+├── YES → Use Native Features (built-in)
+│   └── Enable in Admin Settings, toggle per-chat
+│
+└── NO → Continue...
+
+Do you need custom Python code to run on the server?
+├── YES → Continue...
+│   ├── Is this a simple input/output transformation?
+│   │   ├── YES → Use Functions (Filters/Pipes)
+│   │   └── NO → Use Workspace Tools
+│   │
+│   └── Need to offload heavy processing?
+│       ├── YES → Use Pipelines (separate container)
+│       └── NO → Use Workspace Tools
+│
+└── NO → Continue...
+
+Do you need to connect external services via API?
+├── YES → Use OpenAPI Servers or MCP
+│   ├── Standard REST API? → OpenAPI Server
+│   └── MCP-compatible service? → MCP (via HTTP or MCPO proxy)
+│
+└── NO → You probably don't need tools!
+```
+
+### Common Scenarios
+
+**"I want the AI to search the web"**
+→ Use Native Web Search.
+Enable in Admin > Settings > Web Search.
+Toggle in chat UI.
+No code required.
+
+**"I need a custom weather lookup API"**
+→ Use Workspace Tools.
+Write Python to call weather API.
+Simple, integrated with Open WebUI.
+
+**"I want to filter out PII before sending to AI"**
+→ Use Functions (Filter).
+Transform messages before they reach the model.
+Lightweight processing.
+
+**"I need to run heavy ML models for document classification"**
+→ Use Pipelines.
+Runs in separate container.
+Doesn't slow down main Open WebUI.
+
+**"I want to connect to my company's internal API"**
+→ Use OpenAPI Server.
+Provide OpenAPI spec.
+Automatic tool generation.
+
+**"I have a Claude Desktop MCP server I want to use"**
+→ Use MCP via MCPO.
+Use MCPO proxy to bridge stdio MCP to HTTP.
+Connect in Settings > Connections.
 
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