docs: update tool-adding instructions for auto-discovery

- AGENTS.md: 3 files → 2 files, remove _discover_tools() step
- adding-tools.md: remove Step 3, note auto-discovery
- architecture.md: update discovery description
- tools-runtime.md: replace manual list with discover_builtin_tools() docs
- hermes-agent skill: remove manual import step

website/docs/developer-guide/adding-tools.md

@@ -14,11 +14,12 @@ Make it a **Tool** when it requires end-to-end integration with API keys, custom
 
 ## Overview
 
-Adding a tool touches **3 files**:
+Adding a tool touches **2 files**:
 
 1. **`tools/your_tool.py`** — handler, schema, check function, `registry.register()` call
 2. **`toolsets.py`** — add tool name to `_HERMES_CORE_TOOLS` (or a specific toolset)
-3. **`model_tools.py`** — add `"tools.your_tool"` to the `_discover_tools()` list
+
+Any `tools/*.py` file with a top-level `registry.register()` call is auto-discovered at startup — no manual import list required.
 
 ## Step 1: Create the Tool File
 
@@ -124,19 +125,9 @@ _HERMES_CORE_TOOLS = [
 },
 ```
 
-## Step 3: Add Discovery Import
+## ~~Step 3: Add Discovery Import~~ (No longer needed)
 
-In `model_tools.py`, add the module to the `_discover_tools()` list:
-
-```python
-def _discover_tools():
-    _modules = [
-        ...
-        "tools.weather_tool",  # <-- add here
-    ]
-```
-
-This import triggers the `registry.register()` call at the bottom of your tool file.
+Tool modules with a top-level `registry.register()` call are auto-discovered by `discover_builtin_tools()` in `tools/registry.py`. No manual import list to maintain — just create your file in `tools/` and it's picked up at startup.
 
 ## Async Handlers