# Message Metadata > Annotate user and agent messages with metadata such as their timestamp when they are sent to the LLM, so agents can reason about timing and gaps between messages. Source: | | | | ---------------- | ------------------ | | **ID** | `message_metadata` | | **Category** | Core | | **Features** | None | | **Dependencies** | None | Annotates user and agent messages with metadata, currently each message’s timestamp (UTC), when building the LLM request. The model sees each message prefixed with an annotation like: ```plaintext [time 2026-06-11T09:15:42Z] What changed since yesterday? ``` For user messages the timestamp is when the message was received; for agent messages, when the reply was generated. This lets agents reason about timing: how long ago something was said, gaps between messages, and whether earlier statements are stale. Opt-in on the canonical levels. Included in deprecated Generic and Platform Chat. Annotations are applied only to the prompt-facing view of the conversation. Stored messages are never modified, and timestamps are stable across turns so prompt caching is unaffected. A short system prompt addition explains the annotation format to the model and instructs it not to emit annotations in its replies. ## Tools None. ## Configuration | Field | Type | Default | Description | | -------- | ----- | --------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- | | `fields` | array | `["timestamp"]` | Metadata fields to render, in order. Supported: `timestamp`. An empty array disables annotations. More fields (e.g. the LLM model) will be added over time. | User and agent messages are always annotated; system and tool-result messages never are. ## See Also * [Current Time](https://everruns.com/docs/capabilities/current-time/), tool to get the current wall-clock time * [Capabilities Overview](https://everruns.com/docs/capabilities/)