"Kimi K3 in Hermes Agent: four lines of YAML, verified end-to-end"

Hermes Agent is an open-source CLI agent from Nous Research with tool-calling built in. It supports custom OpenAI-compatible endpoints, which means it can run the kimi-k3 reasoning model from Moonshot AI through any compatible gateway. This guide covers the exact configuration, verified end-to-end on 2026-09-10 against Hermes Agent v0.19.0: chat works, and — the part that actually matters for an agent — tool use works. Disclosure: Wallaby Token sells API access to kimi-k3, and the endpoint below is ours.

What you need

• A Wallaby Token API key (create an account at wallabytoken.com; new accounts receive $0.50 in free credit)
• Hermes Agent installed. We tested the pip route in a virtual environment:

python3 -m venv ~/.hermes-venv
~/.hermes-venv/bin/pip install hermes-agent

Setup

Hermes persists its model configuration in ~/.hermes/config.yaml. Add four lines:

model:
  default: kimi-k3
  provider: custom
  base_url: https://api.wallabytoken.com/v1
  api_key: sk-your-wallaby-key

Note the /v1 suffix on the base URL — it is required here. If you prefer a wizard, hermes model walks you through the same values interactively (choose a custom endpoint, then enter the base URL, API key, and model name) and writes the same file. Both paths converge on the block above; we verified the YAML path directly.

Verify the configuration

Run a one-shot prompt:

hermes -z "What model are you? Reply in one short sentence."

A working setup answers immediately and identifies itself correctly. Our run:

Then verify tool use — a chat reply alone does not prove an agent will work, because many "compatible" endpoints handle plain chat but break on tool calls. From a scratch directory:

hermes --yolo -z "Create a file named palindrome.py containing a function that checks whether a string is a palindrome, plus two test cases. Then stop."

--yolo auto-approves every tool action, so only use it in a directory where anything the agent writes is disposable. For real work, use hermes chat and approve actions one by one. Our run created the file, executed it, and reported the result; we re-ran the generated file ourselves afterwards and the tests passed:

What a Hermes session costs

One thing to know before you budget: Hermes prepends a substantial system prompt — roughly 10,500 input tokens — to every turn. At our promotional rate that is about $0.028 of input per turn before the model says a word, and agent loops multiply it (our single-file tool-use test above made three model calls). Running both verification steps in this guide cost us $0.068 in total. This is normal for full-featured agents, but it makes per-request, itemized billing worth having: every one of those calls appeared on our dashboard with its token counts within seconds.

Pricing

All prices are per 1M tokens.

Post-promotion pricing remains 5% below the official list price. The $0.50 trial credit covers approximately 185,000 input tokens at the promotional rate — enough to complete both verification steps above several times over, bearing in mind the system-prompt overhead described above. The minimum top-up is $20.

Why you can trust a small provider

We operate a public status page so availability can be verified independently rather than taken on faith. Our terms are published in plain language, and we are a registered Australian company with an ABN on file. We also run our own internal workloads through the same gateway we sell, so the service you use is the service we depend on.

What we do differently

Three decisions distinguish Wallaby Token from other resellers. First, billing is transparent and itemized per request, so every charge can be reconciled against actual usage — the cost figures in this article came from our own logs. Second, we host open-weight models only; we do not resell access to closed proprietary models. Third, we do not chase short-lived model hype cycles — we add models when they demonstrate durable value, not when they trend.

Get started

Create an account at wallabytoken.com, receive $0.50 in free trial credit, and generate an API key. Four lines of YAML later, Hermes runs on kimi-k3.