Adding Tools
إضافة أداة جديدة
Start with meaning, then move to detail.
This lesson explains Adding Tools as part of Hermes internals and extension points. You will learn what it does, when it matters, and the smallest safe test that proves it works.
If you are new, do not memorize names. Focus on three questions: what problem does this solve, what access does it need, and how can you verify the result?
For practice, inspect the first example, identify its effects, run it on test data, and compare the result with the source claim.
For advanced readers, inspect Overview, Step 1: Create the Built-in Tool File, Key Rules, then verify failure modes and version compatibility.
Know Python, Git, and basic project structure before changing code.
A clear outcome before you read.
- Understand Adding Tools without assumed prior knowledge.
- Separate the source description from what still needs testing in your environment.
- Read the first command and identify its inputs and outputs before copying it.
Short definitions before the details.
- Tool
- A structured action the agent can call to read or change something.
How to add a new tool to Hermes Agent — schemas, handlers, registration, and toolsets
What does the source say, and in what order?
- 01Overview
Start here to understand the core idea or structure.
- 02Step 1: Create the Built-in Tool File
Read this after the foundation, then connect it to the previous step.
- 03Key Rules
Read this after the foundation, then connect it to the previous step.
- 04Step 2: Add the Built-in Tool to a Toolset
Read this after the foundation, then connect it to the previous step.
- 05~~Step 3: Add Discovery Import~~ (No longer needed)
Read this after the foundation, then connect it to the previous step.
- 06Async Handlers
Read this after the foundation, then connect it to the previous step.
- 07Handlers That Need taskid
Read this after the foundation, then connect it to the previous step.
- 08Agent-Loop Intercepted Tools
Read this after the foundation, then connect it to the previous step.
- 09Optional: Setup Wizard Integration
Read this after the foundation, then connect it to the previous step.
- 10Checklist
Finish here to verify the result and special cases.
Copy only after you understand the effect.
### Key Rules
:::danger Important
- Handlers **MUST** return a JSON string (via `json.dumps()`), never raw dicts
- Errors **MUST** be returned as `{"error": "message"}`, never raised as exceptions
- The `check_fn` is called when building tool definitions — if it returns `False`, the tool is silently excluded
- The `handler` receives `(args: dict, **kwargs)` where `args` is the LLM's tool call arguments
:::
## Step 2: Add the Built-in Tool to a Toolset
In `toolsets.py`, add the tool name:## ~~Step 3: Add Discovery Import~~ (No longer needed)
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
If your handler needs async code, mark it with `is_async=True`:The registry handles async bridging transparently — you never call `asyncio.run()` yourself.
## Handlers That Need task_id
Tools that manage per-session state receive `task_id` via `**kwargs`:Read the first command and identify its inputs and outputs before copying it.
Match every command to your installed Hermes version, review the files and accounts it can reach, and use non-sensitive data for the first test. If this explanation differs from the source, the official source wins.