docs: add README

README.md

@@ -1,3 +1,138 @@
 # gnmi-eos
 
-gNMI CLI tool and Python library for Arista EOS devices — get, set, subscribe, discover YANG paths
+gNMI CLI tool and Python library for Arista EOS devices.
+
+Interact with Arista EOS devices via gNMI/YANG: get configuration and state, push changes, subscribe to counters and events.
+
+## Features
+
+- **CLI** — usable via `uvx gnmi-eos` or installed globally
+- **Library** — importable as `from gnmi_eos import GNMIClient`
+- **Validated YANG paths** for EOS 4.35.0F (OpenConfig + Arista experimental models)
+
+## Installation
+
+```bash
+# As a CLI tool with uvx (no install needed)
+uvx --from git+https://gitea.arnodo.fr/Damien/gnmi-eos gnmi-eos --help
+
+# Or install permanently
+uv tool install git+https://gitea.arnodo.fr/Damien/gnmi-eos
+```
+
+## CLI Usage
+
+Credentials can be passed as options or via environment variables:
+
+```bash
+export GNMI_TARGET=leaf1:6030
+export GNMI_USERNAME=admin
+export GNMI_PASSWORD=admin
+```
+
+### Get capabilities
+
+```bash
+gnmi-eos capabilities --target leaf1:6030
+```
+
+### Get data
+
+```bash
+# Get interface state
+gnmi-eos get --target leaf1:6030 --path "/interfaces/interface[name=Ethernet1]/state"
+
+# Get config only
+gnmi-eos get --target leaf1:6030 --path "/interfaces" --type config
+
+# Output as raw JSON or save to file
+gnmi-eos get --target leaf1:6030 --path "/" --output json
+gnmi-eos get --target leaf1:6030 --path "/" --output file:dump.json
+```
+
+### Subscribe
+
+```bash
+# Subscribe to interface state changes (on-change)
+gnmi-eos subscribe --target leaf1:6030 \
+    --path "/interfaces/interface/state/oper-status" \
+    --mode on-change
+
+# Sample interface counters every 10s
+gnmi-eos subscribe --target leaf1:6030 \
+    --path "/interfaces/interface[name=Ethernet1]/state/counters" \
+    --mode sample --interval 10
+
+# Multiple paths, stop after 5 updates
+gnmi-eos subscribe --target leaf1:6030 \
+    --path "/interfaces/interface/state/oper-status" \
+    --path "/network-instances/network-instance[name=default]/protocols/protocol[identifier=BGP][name=BGP]/bgp/neighbors/neighbor/state/session-state" \
+    --count 5
+```
+
+### Set configuration
+
+```bash
+# Dry-run (default — safe)
+gnmi-eos set --target leaf1:6030 \
+    --path "/interfaces/interface[name=Ethernet1]/config/description" \
+    --value "Uplink to Spine"
+
+# Actually apply
+gnmi-eos set --target leaf1:6030 \
+    --path "/interfaces/interface[name=Ethernet1]/config/description" \
+    --value "Uplink to Spine" \
+    --no-dry-run
+```
+
+### Show known YANG paths
+
+```bash
+gnmi-eos paths
+```
+
+## Library Usage
+
+```python
+from gnmi_eos import GNMIClient
+from gnmi_eos.yang.paths import Interfaces, BGP, FabricSubscriptions
+
+with GNMIClient(host="leaf1", port=6030, username="admin", password="admin") as client:
+    # Get capabilities
+    caps = client.capabilities()
+
+    # Get interface counters
+    counters = client.get(Interfaces.counters("Ethernet1"))
+
+    # Get BGP neighbor state
+    state = client.get(BGP.neighbor_state("10.0.0.1"))
+
+    # Subscribe to interface changes
+    for update in client.subscribe(
+        paths=[str(FabricSubscriptions.INTERFACE_STATE)],
+        stream_mode="on-change",
+    ):
+        print(update)
+```
+
+## YANG Models
+
+Validated against **Arista EOS 4.35.0F** with ContainerLab (cEOS).
+
+| Category | Model |
+|----------|-------|
+| Interfaces, VLANs, BGP | `openconfig-*` |
+| VXLAN | `arista-exp-eos-vxlan` |
+| MLAG | `arista-exp-eos-mlag` |
+| EVPN | `arista-exp-eos-evpn` |
+
+> **Note:** MLAG and EVPN state (peer status, learned routes) is not exposed via gNMI — use eAPI for operational state.
+
+## Subscription Notes
+
+For Arista EOS, use native paths **without** module prefixes for `ON_CHANGE` subscriptions:
+
+```
+✅  /interfaces/interface[name=Ethernet1]/state
+❌  /openconfig-interfaces:interfaces/...
+```