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Cron: isolated jobs fail with 'Field required' on tools.function

Work around isolated cron job failures that reject tool definitions with `Field required` on `tools.function` by temporarily switching the job to the main-session systemEvent path.

By CoClaw Team • March 8, 2026

Symptoms

A cron job is configured with sessionTarget: "isolated".
The run fails before the agent turn really starts.
Logs or run details show validation errors like:
- Field required
- tools.function
This usually appears on jobs using payload.kind: "agentTurn".

Cause

This is usually a regression in the isolated cron session path, not a bad prompt.

Main-session cron jobs and isolated cron jobs do not go through exactly the same execution path:

sessionTarget: "main" uses a systemEvent payload routed through the main heartbeat/session flow.
sessionTarget: "isolated" uses a dedicated isolated agent-turn path.

In affected versions, the isolated path can reject tool definitions with a stricter or mismatched schema expectation, so the run fails on tools[*].function before normal execution begins.

Fix

1) Move the job to the main session temporarily

Edit the job so it runs on the main session instead of the isolated one:

openclaw cron edit <job-id> --session main --system-event "<your existing prompt text>"

If the job was previously created with --message, convert that message into the --system-event text you want the main agent to receive.

Why this helps: the main-session systemEvent path avoids the isolated tool-schema validation path that is currently failing.

2) If the job had announce delivery enabled, disable it while testing

openclaw cron edit <job-id> --no-deliver

Why this helps: announce delivery is only relevant to isolated-style output delivery. Turning it off removes one extra moving part while you verify the core cron run works again.

3) Run the job manually and inspect run history

openclaw cron run <job-id>
openclaw cron runs --id <job-id> --limit 20

If the job must remain isolated long-term, keep the old config notes somewhere safe and switch back only after the upstream fix lands.

Verify

openclaw cron run <job-id> completes without the tools.function validation error.
openclaw cron runs --id <job-id> --limit 20 shows a successful run.
The job now leaves evidence in the main session path (system event, output artifact, explicit message, or whatever your workflow expects).

If it still fails after switching to main + systemEvent, collect:

openclaw cron get <job-id> output,
the latest openclaw cron runs --id <job-id> --limit 20,
and the exact validation error text.

That usually means the problem is no longer isolated to the isolated-session path.