Agentbill

A preflight gate for AI agent runs. Stop runaway loops before they start.

CI PyPI npm License: MIT

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Budget exceeded? GPU quota hit? Free tier exhausted? AgentBill blocks the run before the first token — not after the damage is done.

Works whether you're paying OpenAI per token or running your own GPU.

"The moment you're using Stripe as your safety net, you've already lost the run." — scarlett1908, r/LangChain

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Install

Python:

pip install agentbill-sdk

Node.js:

npm install agentbill

Quick Start

from agentbill import AgentBillClient

client = AgentBillClient(api_key="agb_your_key")

check = client.preflight(agent_id="researcher", estimated_units=10)
if not check.approved:
    raise Exception(f"Blocked: {check.reason}")

# run your agent here

client.record(agent_id="researcher", units=10)

Get your API key: https://agentbill.fly.dev/register

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What it does

Preflight. Before the agent runs, AgentBill checks: does this customer have enough budget? If not, block it before any compute is consumed.

Per-request ceiling. Monthly caps do not catch the bad single run. One 3-hour research loop can blow your budget before the cap triggers. AgentBill enforces a ceiling at the invocation level.

Outcome-based metering. You define what counts as a billable event. Not bytes, not seconds. The business-level action the agent performed.

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Free tier

1,000 preflight calls/month. No credit card required.

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When to use AgentBill

• Add billing to a LangChain agent — wrap any chain with preflight() + record(). Two calls.
• Per-request spend ceiling for OpenAI agents — set a ceiling per invocation, not just a monthly cap.
• Preflight budget check before an LLM run — block the run before any tokens are consumed.
• Agent cost control in Python or Node.js — SDK available for both.
• Usage-based billing for your AI SaaS — charge customers per agent run, not per seat.

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What it does NOT do

• Multi-step workflows with state machines or reversal logic (out of scope)
• Replace your payment processor (AgentBill sits in front of it)
• No-code dashboard for non-developers

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Why not Stripe

	Stripe	AgentBill
Preflight block	No	Yes
Per-request ceiling	No	Yes
Blocks before compute	No	Yes
Built for agents	No	Yes

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MCP Server

AgentBill ships an MCP server for native integration with Claude Code, Cursor, Windsurf, and any MCP-compatible agent host.

uvx agentbill-mcp

The MCP server exposes two tools:

• preflight(agent_id, customer_id, estimated_units, ceiling) — check budget before running. Blocks if exhausted.
• record_event(agent_id, units, customer_id, metadata) — bill after work completes.

Configure in ~/.claude/settings.json:

{
  "mcpServers": {
    "agentbill": {
      "command": "uvx",
      "args": ["agentbill-mcp"],
      "env": { "AGENTBILL_API_KEY": "sk_live_..." }
    }
  }
}

Source: mcp/ | PyPI: agentbill-mcp

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Tech Stack

Layer	Technology
Backend API	Node.js 20, TypeScript, Fastify
Deployment	Fly.io, Docker
Billing	Polar
Python SDK	agentbill-sdk on PyPI
Node.js SDK	agentbill on npm
MCP Server	agentbill-mcp on PyPI

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Local Dev

Prerequisites: Node.js 20+, Python 3.10+

git clone https://github.com/marketinglior-pixel/agentbill.git
cd agentbill
npm install
cp .env.example .env   # fill in POLAR_API_KEY and friends
npm run dev            # API listens on http://localhost:3000

Run the smoke test suite (requires the dev server running):

./test_live.sh

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Contributing

Contributions are welcome. See CONTRIBUTING.md for setup instructions, code style, and how to open a PR.

Looking for something to work on? Check the good first issue label.

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Star this repo

If per-request ceilings are what you needed, star this. It helps other developers find it.