Personalization Sub-Agent Pattern

Cold email personalization at scale requires per-lead generation. Claude Code's Task tool lets you fan out to many sub-agents in parallel, each personalizing a slice of the lead list. This skill defines the reusable approval-loop pattern.

Always Task tool — never an API key

This skill runs entirely inside Claude Code via the Task tool. No Anthropic SDK calls, no OpenAI calls. This is intentional:

• No extra API spend. Uses your Claude Code plan.
• No key management. Works out of the box.
• Parallel by design. Claude Code spawns multiple Task sub-agents in one message, letting 100 leads finish in the time it takes to personalize 10.

At very large scale (1,000+ leads), the tuned prompt can optionally be shipped to the Anthropic API for throughput. But TUNING and normal campaign runs (under 500 leads) always go through the Task tool.

The approval loop (before full fan-out)

Don't personalize 500 leads and then discover the prompt is wrong. Loop first, then scale.

Round 0 — Sample on 1 lead