docs: expand README with usage, schema, labels, errors, env vars

README.md

@@ -1,2 +1,70 @@
 # miti-loki
-A Cloudflare Worker that forward message to [My Grafana Cloud](https://miti99.grafana.net)'s Loki
+
+A Cloudflare Worker that forwards logs to [My Grafana Cloud](https://miti99.grafana.net)'s Loki.
+
+## Usage
+
+POST a JSON body to `https://miti-loki.miti99.workers.dev/`. GET redirects to this repo. Any other method returns 405; missing/empty body returns 400.
+
+### Single log entry
+
+```bash
+curl -X POST 'https://miti-loki.miti99.workers.dev/?app=demo&env=prod' \
+  -H 'Content-Type: application/json' \
+  -d '{"message": "Hello from miti-loki"}'
+```
+
+### Batch (array of entries)
+
+```bash
+curl -X POST 'https://miti-loki.miti99.workers.dev/?app=demo' \
+  -H 'Content-Type: application/json' \
+  -d '[{"message":"first"},{"message":"second"}]'
+```
+
+### Body schema
+
+Each entry is `{message, timestamp?, metadata?}`:
+
+- `message` (string, required) — log line.
+- `timestamp` (string, optional) — Unix nanoseconds. Defaults to current time.
+- `metadata` (object, optional) — flat key-value pairs (no nested objects). Forwarded as Loki structured metadata.
+
+### Stream labels
+
+URL query params become Loki stream labels. Label names must match `[a-zA-Z_:][a-zA-Z0-9_:]*` and cannot both start and end with `_` (reserved). Invalid labels return 400.
+
+Two labels are auto-injected (overwriting any caller-supplied values):
+
+- `proxy=miti-loki`
+- `ip=<client-ip>` (from `CF-Connecting-IP` / `X-Forwarded-For`)
+
+### Errors
+
+- `400` — empty body, invalid JSON, missing `message`, nested metadata, or invalid label name.
+- `405` — non-POST/GET/OPTIONS method.
+- `500` — worker missing `LOKI_HOST` / `LOKI_USERNAME` / `LOKI_PASSWORD` env vars (deploy-time issue, not caller-fixable), or upstream fetch error.
+- Otherwise the response status, body, and content-type are passed through from Loki's `/loki/api/v1/push`.
+
+Responses are CORS-permissive (`Access-Control-Allow-Origin: *`, `POST, OPTIONS` allowed).
+
+### Env vars (deploy-time)
+
+- `LOKI_HOST` — Loki host (e.g. `logs-prod-XXX.grafana.net`).
+- `LOKI_USERNAME` — Basic Auth user (Grafana Cloud instance ID).
+- `LOKI_PASSWORD` — Basic Auth password (Grafana Cloud API token).
+- `LOKI_PORT` (optional) — defaults to `443` (HTTPS). Any other value uses HTTP.
+
+### For AI agents / Claude Code routines
+
+Read this section first, do not probe.
+
+- **One POST per intended log batch.** Do not send a `"test"` payload to verify the endpoint — every successful POST writes to Loki, so probes pollute the log stream.
+- **Exact request:**
+  ```
+  POST https://miti-loki.miti99.workers.dev/?<label>=<value>&...
+  Content-Type: application/json
+  {"message": "<your log>"}
+  ```
+- **Success:** any 2xx (typically 204 from Loki). **Auth-related errors:** 500 (env vars missing — deploy-time issue).
+- **Do not retry on 2xx.** Each POST is a separate ingest; a retry would duplicate log lines.