diff --git a/docs/gateway/configuration-reference.md b/docs/gateway/configuration-reference.md
index f428a20546a..209427ca277 100644
--- a/docs/gateway/configuration-reference.md
+++ b/docs/gateway/configuration-reference.md
@@ -722,7 +722,8 @@ Time format in system prompt. Default: `auto` (OS preference).
   - String form sets only the primary model.
   - Object form sets primary plus ordered failover models.
 - `imageModel`: accepts either a string (`"provider/model"`) or an object (`{ primary, fallbacks }`).
-  - Only used if the selected/default model cannot accept image input.
+  - Used by the `image` tool path as its vision-model config.
+  - Also used as fallback routing when the selected/default model cannot accept image input.
 - `model.primary`: format `provider/model` (e.g. `anthropic/claude-opus-4-6`). If you omit the provider, OpenClaw assumes `anthropic` (deprecated).
 - `models`: the configured model catalog and allowlist for `/model`. Each entry can include `alias` (shortcut) and `params` (provider-specific: `temperature`, `maxTokens`).
 - Config writers that mutate these fields (for example `/models set`, `/models set-image`, and fallback add/remove commands) save canonical object form and preserve existing fallback lists when possible.