---
id: RT-TOOL-4
family: RT-TOOL
level: extended
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/rt-tool/rt-tool-4
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# RT-TOOL-4 — A turn's artifacts are persisted on its message and reported on its result

*RT-TOOL (Part II) · level: extended · profiles: runtime · added in 1.0*

## The rule

> **Normative.** This is the rule.
>
> 1. The artifacts a run collected are persisted on the last assistant message that run wrote, once per run.
>
> 2. A turn's result aggregates the persisted artifacts of every assistant message in the turn, so they survive a reload, and the turn API reports the same list.
>
> 3. On the wire a message carries them as a top-level `toolArtifacts` field rather than as raw message metadata.


## What it means

Artifacts are not a run-scoped, in-memory extra that a reload would lose:
they land on the assistant message itself, so reading the turn back later
still returns them. A caller reading the wire form never sees the storage
key they were kept under — they arrive as their own top-level field, not
nested inside the message's general metadata, so a client does not have to
know the internal name to find them.

## Example

```json title="An artifact a tool call produced during the turn" verdict="produced"
{ "type": "link", "payload": { "url": "https://example.com/report" }, "tool_call_id": "call_1" }
```

```json title="The assistant message as the door reports it" verdict="reported"
{
  "toolArtifacts": [
    { "type": "link", "payload": { "url": "https://example.com/report" }, "tool_call_id": "call_1" }
  ],
  "metadata": {}
}
```

The message's `metadata` never carries the artifacts under their storage
key — a client that only reads `toolArtifacts` sees everything there is to
see.

## Related rules

- Names: RT-TOOL-3, RT-TOOL-7
- Referenced by: RT-TOOL-3, RT-TOOL-7

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.