fix: document tools invoke + honor main session key (#1575) (thanks @vignesh07)

docs/gateway/tools-invoke-http-api.md

@@ -0,0 +1,79 @@
+---
+summary: "Invoke a single tool directly via the Gateway HTTP endpoint"
+read_when:
+  - Calling tools without running a full agent turn
+  - Building automations that need tool policy enforcement
+---
+# Tools Invoke (HTTP)
+
+Clawdbot’s Gateway exposes a simple HTTP endpoint for invoking a single tool directly. It is always enabled, but gated by Gateway auth and tool policy.
+
+- `POST /tools/invoke`
+- Same port as the Gateway (WS + HTTP multiplex): `http://<gateway-host>:<port>/tools/invoke`
+
+Default max payload size is 2 MB.
+
+## Authentication
+
+Uses the Gateway auth configuration. Send a bearer token:
+
+- `Authorization: Bearer <token>`
+
+Notes:
+- When `gateway.auth.mode="token"`, use `gateway.auth.token` (or `CLAWDBOT_GATEWAY_TOKEN`).
+- When `gateway.auth.mode="password"`, use `gateway.auth.password` (or `CLAWDBOT_GATEWAY_PASSWORD`).
+
+## Request body
+
+```json
+{
+  "tool": "sessions_list",
+  "action": "json",
+  "args": {},
+  "sessionKey": "main",
+  "dryRun": false
+}
+```
+
+Fields:
+- `tool` (string, required): tool name to invoke.
+- `action` (string, optional): mapped into args if the tool schema supports `action` and the args payload omitted it.
+- `args` (object, optional): tool-specific arguments.
+- `sessionKey` (string, optional): target session key. If omitted or `"main"`, the Gateway uses the configured main session key (honors `session.mainKey` and default agent, or `global` in global scope).
+- `dryRun` (boolean, optional): reserved for future use; currently ignored.
+
+## Policy + routing behavior
+
+Tool availability is filtered through the same policy chain used by Gateway agents:
+- `tools.profile` / `tools.byProvider.profile`
+- `tools.allow` / `tools.byProvider.allow`
+- `agents.<id>.tools.allow` / `agents.<id>.tools.byProvider.allow`
+- group policies (if the session key maps to a group or channel)
+- subagent policy (when invoking with a subagent session key)
+
+If a tool is not allowed by policy, the endpoint returns **404**.
+
+To help group policies resolve context, you can optionally set:
+- `x-clawdbot-message-channel: <channel>` (example: `slack`, `telegram`)
+- `x-clawdbot-account-id: <accountId>` (when multiple accounts exist)
+
+## Responses
+
+- `200` → `{ ok: true, result }`
+- `400` → `{ ok: false, error: { type, message } }` (invalid request or tool error)
+- `401` → unauthorized
+- `404` → tool not available (not found or not allowlisted)
+- `405` → method not allowed
+
+## Example
+
+```bash
+curl -sS http://127.0.0.1:18789/tools/invoke \
+  -H 'Authorization: Bearer YOUR_TOKEN' \
+  -H 'Content-Type: application/json' \
+  -d '{
+    "tool": "sessions_list",
+    "action": "json",
+    "args": {}
+  }'
+```