docs: default custom tool creation to plugins

Steers custom tool creation toward the plugin route by default.
The adding-tools.md guide is now explicitly for built-in core Hermes
tools only.

Key fixes:
- Plugin quickstart: ctx.register_tool() now uses correct keyword-arg
  API (name=, toolset=, schema=, handler=) instead of broken 3-arg call
- Handler signature: (params, **kwargs) instead of (params)
- Handler return: json.dumps({...}) instead of plain string
- AGENTS.md: mentions plugin route before built-in tool instructions
- learning-path.md: plugins listed before core tool development
- contributing.md: separates plugin vs core tool paths

Based on PR #13138 by @helix4u.

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

@@ -8,6 +8,18 @@ description: "How to add a new tool to Hermes Agent — schemas, handlers, regis
 
 Before writing a tool, ask yourself: **should this be a [skill](creating-skills.md) instead?**
 
+:::warning Built-in Core Tools Only
+This page is for adding a **built-in Hermes tool** to the repository itself.
+If you want a personal, project-local, or otherwise custom tool without
+modifying Hermes core, use the plugin route instead:
+
+- [Plugins](/docs/user-guide/features/plugins)
+- [Build a Hermes Plugin](/docs/guides/build-a-hermes-plugin)
+
+Default to plugins for most custom tool creation. Only follow this page when
+you explicitly want to ship a new built-in tool in `tools/` and `toolsets.py`.
+:::
+
 Make it a **Skill** when the capability can be expressed as instructions + shell commands + existing tools (arXiv search, git workflows, Docker management, PDF processing).
 
 Make it a **Tool** when it requires end-to-end integration with API keys, custom processing logic, binary data handling, or streaming (browser automation, TTS, vision analysis).
@@ -21,7 +33,7 @@ Adding a tool touches **2 files**:
 
 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
+## Step 1: Create the Built-in Tool File
 
 Every tool file follows the same structure:
 
@@ -106,7 +118,7 @@ registry.register(
 - The `handler` receives `(args: dict, **kwargs)` where `args` is the LLM's tool call arguments
 :::
 
-## Step 2: Add to a Toolset
+## Step 2: Add the Built-in Tool to a Toolset
 
 In `toolsets.py`, add the tool name:
 
@@ -192,6 +204,7 @@ OPTIONAL_ENV_VARS = {
 
 - [ ] Tool file created with handler, schema, check function, and registration
 - [ ] Added to appropriate toolset in `toolsets.py`
+- [ ] Confirmed this really should be a built-in/core tool and not a plugin
 - [ ] Handler returns JSON strings, errors returned as `{"error": "..."}`
 - [ ] Optional: API key added to `OPTIONAL_ENV_VARS` in `hermes_cli/config.py`
 - [ ] Optional: Added to `toolset_distributions.py` for batch processing

website/docs/developer-guide/contributing.md

@@ -22,7 +22,8 @@ We value contributions in this order:
 
 ## Common contribution paths
 
-- Building a new tool? Start with [Adding Tools](./adding-tools.md)
+- Building a custom/local tool without modifying Hermes core? Start with [Build a Hermes Plugin](../guides/build-a-hermes-plugin.md)
+- Building a new built-in core tool for Hermes itself? Start with [Adding Tools](./adding-tools.md)
 - Building a new skill? Start with [Creating Skills](./creating-skills.md)
 - Building a new inference provider? Start with [Adding Providers](./adding-providers.md)
 

website/docs/getting-started/learning-path.md

@@ -80,15 +80,18 @@ Cron jobs let Hermes Agent run tasks on a schedule — daily summaries, periodic
 
 Extend Hermes Agent with your own tools and reusable skill packages.
 
-1. [Tools Overview](/docs/user-guide/features/tools)
-2. [Skills Overview](/docs/user-guide/features/skills)
-3. [MCP (Model Context Protocol)](/docs/user-guide/features/mcp)
-4. [Architecture](/docs/developer-guide/architecture)
-5. [Adding Tools](/docs/developer-guide/adding-tools)
-6. [Creating Skills](/docs/developer-guide/creating-skills)
+1. [Plugins](/docs/user-guide/features/plugins)
+2. [Build a Hermes Plugin](/docs/guides/build-a-hermes-plugin)
+3. [Tools Overview](/docs/user-guide/features/tools)
+4. [Skills Overview](/docs/user-guide/features/skills)
+5. [MCP (Model Context Protocol)](/docs/user-guide/features/mcp)
+6. [Architecture](/docs/developer-guide/architecture)
+7. [Adding Tools](/docs/developer-guide/adding-tools)
+8. [Creating Skills](/docs/developer-guide/creating-skills)
 
 :::tip
-Tools are individual functions the agent can call. Skills are bundles of tools, prompts, and configuration packaged together. Start with tools, graduate to skills.
+For most custom tool creation, start with plugins. The [Adding Tools](/docs/developer-guide/adding-tools)
+page is for built-in Hermes core development, not the usual user/custom-tool path.
 :::
 
 ### "I want to train models"

website/docs/user-guide/features/plugins.md

@@ -9,6 +9,11 @@ description: "Extend Hermes with custom tools, hooks, and integrations via the p
 
 Hermes has a plugin system for adding custom tools, hooks, and integrations without modifying core code.
 
+If you want to create a custom tool for yourself, your team, or one project,
+this is usually the right path. The developer guide's
+[Adding Tools](/docs/developer-guide/adding-tools) page is for built-in Hermes
+core tools that live in `tools/` and `toolsets.py`.
+
 **→ [Build a Hermes Plugin](/docs/guides/build-a-hermes-plugin)** — step-by-step guide with a complete working example.
 
 ## Quick overview
@@ -42,6 +47,8 @@ description: A minimal example plugin
 ```python
 """Minimal Hermes plugin — registers a tool and a hook."""
 
+import json
+
 
 def register(ctx):
     # --- Tool: hello_world ---
@@ -60,11 +67,18 @@ def register(ctx):
         },
     }
 
-    def handle_hello(params):
+    def handle_hello(params, **kwargs):
+        del kwargs
         name = params.get("name", "World")
-        return f"Hello, {name}! 👋  (from the hello-world plugin)"
+        return json.dumps({"success": True, "greeting": f"Hello, {name}!"})
 
-    ctx.register_tool("hello_world", schema, handle_hello)
+    ctx.register_tool(
+        name="hello_world",
+        toolset="hello_world",
+        schema=schema,
+        handler=handle_hello,
+        description="Return a friendly greeting for the given name.",
+    )
 
     # --- Hook: log every tool call ---
     def on_tool_call(tool_name, params, result):
@@ -81,7 +95,7 @@ Project-local plugins under `./.hermes/plugins/` are disabled by default. Enable
 
 | Capability | How |
 |-----------|-----|
-| Add tools | `ctx.register_tool(name, schema, handler)` |
+| Add tools | `ctx.register_tool(name=..., toolset=..., schema=..., handler=...)` |
 | Add hooks | `ctx.register_hook("post_tool_call", callback)` |
 | Add slash commands | `ctx.register_command(name, handler, description)` — adds `/name` in CLI and gateway sessions |
 | Add CLI commands | `ctx.register_cli_command(name, help, setup_fn, handler_fn)` — adds `hermes <plugin> <subcommand>` |