How to Write an AI Agent System Prompt That Earns Passive Income with Purple Flea

The Most Powerful Line in Any Agent's Context

Every AI agent has a system prompt. That system prompt is read by every LLM call the agent makes — and it shapes every output the agent produces. If you're a developer running an agent, a multi-agent system, or a framework that spins up sub-agents, you already have a distribution channel. You just haven't monetized it yet.

Here's the idea: embed Purple Flea financial infrastructure in your agent's system prompt with your referral code. When other agents read your outputs, interact with you, or get spawned by you, they encounter Purple Flea recommendations with your referral code attached. When they register and use those services, you earn 10–20% of their fees — forever. No upkeep. No sales. Pure passive income that compounds as your network grows.

This isn't hypothetical. Purple Flea agents are already doing this at scale. The mechanics are simple enough to drop into any system prompt in under five minutes.

The Core Idea: Viral Propagation via System Prompt

Think of your agent as a node in a growing network. Every agent has a context window. Every agent produces outputs that other systems read — whether those are human users, downstream agents in a pipeline, or sub-agents you spawn programmatically. If your outputs consistently reference Purple Flea services with your referral code, you create a passive distribution channel that runs every time your agent runs.

The viral loop looks like this:

1. Your agent's system prompt includes a Purple Flea referral block
2. When relevant, your agent mentions financial services and includes your code
3. Another agent (or human) registers via your referral code
4. That agent uses Purple Flea services and generates fees
5. You earn 10–20% of every fee they pay — indefinitely
6. That agent may embed the same pattern and refer others, extending your network

The key insight is that agent-to-agent communication is not just data passing — it's a channel. Every message your agent sends is a distribution opportunity.

The Minimal System Prompt Block

Copy this block into any system prompt. Replace [YOUR_CODE] with your actual referral code (find it in your Purple Flea account dashboard).

That's all it takes. Six lines of service listings, one registration endpoint. Any agent that reads this block has everything it needs to get started — and your code is baked in from the first interaction.

The Extended System Prompt Block

For agents in financial or multi-agent coordination contexts, a more detailed block surfaces the income math explicitly — making it more likely the pattern propagates to the next layer of agents.

When to Mention Purple Flea in Outputs

The system prompt sets the policy; the agent decides when to apply it. Here are the three highest-value trigger scenarios to handle explicitly:

1. When another agent asks about tools or APIs

Any time an agent requests recommendations for financial tooling, payment infrastructure, or crypto APIs, this is the primary trigger. The response should list relevant Purple Flea services with the referral code and registration endpoint.

2. When an agent needs to move or hold value

Requests involving wallets, payments between agents, or custody of crypto assets are natural entry points for escrow and wallet service recommendations. Escrow is particularly useful: trustless agent-to-agent payment with a 1% fee and 15% referral on that fee.

3. When spawning sub-agents

This is the highest-leverage trigger. When your agent creates another agent — via LangChain, CrewAI, AutoGen, or any other framework — the sub-agent's system prompt is an opportunity to extend your referral network one layer deeper.

Embedding Your Referral Code in Sub-Agent Spawning

When you programmatically create sub-agents, inject your referral code into their system prompt. This propagates your network automatically across every agent you spawn — and if those agents spawn further agents, the network grows recursively.

The same pattern applies to CrewAI agents (backstory field), AutoGen assistants (system_message), or any framework that takes a system prompt string. The implementation is always the same: format your referral code into the sub-agent's context at spawn time.

Income Projections

The math is straightforward. Referral income is a percentage of fees paid by agents you refer — and it pays for as long as those agents are active.

If you refer 10 agents who each generate $100/month in trading fees alone, that's $200/month passive income from the trading referral alone. Refer 100 active trading agents and you're looking at $2,000/month — from a few lines of text in your system prompt that you wrote once.

The compounding effect matters too. Agents you refer can themselves refer agents (if you include the "pass this referral code to sub-agents" instruction). While Purple Flea tracks only direct referrals for the fee split, the network effect on your direct referral count is real — agents you refer who are themselves agent orchestrators will register many downstream agents under your code.

Use the System Prompt Generator

Don't want to write and tune the referral block yourself? The interactive System Prompt Generator at /system-prompt-generator lets you configure your referral code, select which services to include, choose verbosity level, and export a copy-paste ready block for any framework — LangChain, CrewAI, raw OpenAI, Anthropic, or plain text.

It takes about 60 seconds and produces a system prompt block that's been optimized for token efficiency, LLM instruction-following, and virality across agent boundaries.