Economic Firewall for AI Agents
Keep your AI agents within budget on the paid services they use. Make external agents pay before they use yours. SatGate signs a receipt when it refuses an agent over a budget, a missing payment or a tool permission, and when an agent spends from a budget in Control.
SatGate has three controls. Observe shows what your agents do and spend. Control enforces their budgets. Admit decides what external agents can reach and charges them where you choose. Control and Admit sign receipts, and Observe can too.
Definition
An economic firewall sits in front of your API and decides, for each AI agent request, whether it can go through: is the agent allowed, does it have budget left, and has it paid if the route charges?
It works like an API gateway, plus the parts agent traffic needs and a normal gateway lacks: knowing which agent is calling, per-agent permissions and budgets, revokes, payment, and signed receipts for budget spends and for refusals over a budget, a missing payment or a tool permission.
Where the idea came from
It started with one rule: an external agent pays before it uses your API. That makes abusing your API expensive. It raises the cost of an attack; it does not make one impossible.
The same idea works for your own agents. Each one gets a budget and a list of what it may do, and SatGate checks both before a request runs. Observe shows usage without blocking; Control enforces the limits. Your own agents don't pay anyone. They spend from the budget you set.
Make SatGate the only way to reach your API, and keep your API keys behind it, so agents can't go around it.
Receipts on HTTP and MCP. SatGate signs a receipt when it refuses an agent over a budget, a missing payment or a tool permission, and when an agent spends from a budget in Control. This covers HTTP APIs and MCP tools, and anyone can check the receipts. A receipt shows what SatGate decided. It is not a compliance certificate.
The problem: agents act faster than anyone can review
Most API security assumes a person or a predictable app is behind each request. Agents plan, retry, hand work to other agents, call tools and loop. Every step can cost money, move data or widen what the agent can reach.
Rate limits can slow traffic. Dashboards can explain yesterday's bill. Neither can answer the question that matters before a request happens: is this agent allowed to take this action right now?
An external agent can run up your costs on purpose. Your own agent can burn through a budget by accident, through retries or handoffs. Both need limits that are checked before each request, and the limits have to hold whether or not the agent wants them.
What it checks on every request
What it controls
On every request, SatGate identifies the agent, checks your rules and allows or refuses it.
Agent identity
Know which agent, sub-agent, token, route and tool is behind every call.
Access control
Allow or block each request, and honor expiry and revokes, before it reaches your API.
Budgets and limits
Set budgets per agent and per tool. The limits travel inside the agent’s token.
Receipts
SatGate signs a receipt when it refuses an agent over a budget, a missing payment or a tool permission, and when an agent spends from a budget in Control. Each receipt shows why a request was refused or what it cost. Export them as Evidence Packs.
Paid access for external agents
On the routes you choose, external agents pay before their request goes through. Paying never gets them past your access rules.
Payment and permission
Paying never gets an agent past your rules
An external agent might pay and still ask for something you have ruled out. SatGate checks both: the agent has to pay where you charge, and it has to stay within what you allow.
SatGate makes that call before it forwards the request, so a refused request never reaches your API.
Payment never widens what an agent can do. A receipt records what SatGate decided, not whether your API's answer was any good.
Guides on agent payments
Observe
Start by watching agent traffic without blocking anything. See usage and cost by agent, model, route, tool, team and workflow, so security, finance and platform teams all see the same numbers.
Control
Then enforce limits on the risky routes: permissions, budgets, expiry and revokes, all checked before your API is called. When SatGate blocks a request, the receipt says why.
Admit
Admit lets external agents in on your terms. On paid routes they pay before the request goes through, and your access rules and revokes still apply to agents that paid.
Developer details: payments and internal budgets
Paid routes use L402 (Lightning), x402 (USDC on Base), or both. L402 pairs a Lightning invoice with an access token. Fiat402 is internal budget control, not a payment rail: when your own agent spends, SatGate subtracts from its budget and no money moves.
Economic firewall vs. the usual controls
Implementation path
How to roll out an economic firewall
Pick one workload and put SatGate in front of it. Check that agents still get their work done, that refusals happen when they should, and that nothing reaches your API without going through SatGate. Observe alone doesn't block anything.
See what your agents do
List which agents, sub-agents, routes, models and MCP tools are in use, and what they cost, before you change anything.
Read this stepSet limits
Turn on Control for the risky routes: budget caps, narrower tokens, expiry and revokes.
Read this stepCharge external agents
Decide what external agents can reach and which routes they pay for. SatGate signs a receipt when it refuses an agent over a budget, a missing payment or a tool permission, and when an agent spends from a budget in Control.
Read this stepFree tools
Check your setup
Free tools to put numbers on the risk and write your first policies.
Related topics
Rules and Receipts
How budget spends, and refusals over a budget, a missing payment or a tool permission, become signed receipts.
MCP
Budgets and permissions for MCP tools. When a receipt signer is configured, a priced call and a budget or tool-permission refusal get a signed receipt.
Control AI agents
Budgets and permissions for your own agents, with receipts you can export.
Agent control plane
Permissions, handoffs, spend, audit and revokes for large fleets of agents.
MCP governance
Budgets, revokes and receipts for MCP tool calls.
Agent API governance
Identity, handoffs, revokes and audit for agent API calls.
AI agent cost control
Stop runaway agent spend with hard budgets.
AI API budget enforcement
Check the budget before a model, tool or API call goes out.
Agent spending limits
Spending caps by task, workflow, sub-agent, route, model and tool.
MCP cost control
Control paid tool calls, retries, SaaS actions, cloud tasks, and data lookups.
Agent payment controls
Rules for agent wallets, budgets and 402 payment requests.
HTTP 402 for AI agents
Understand payment challenges, shared payment tokens, and L402.
L402 agent payments
How L402 ties a Lightning payment to API access.
FAQ
Economic firewall questions
What is an economic firewall?
A gateway that checks each AI agent request before it reaches your API. Your own agents spend from budgets you set. External agents must follow your access rules and, on paid routes, pay first.
How is an economic firewall different from rate limiting?
Rate limiting counts requests. An economic firewall also knows which agent is calling, what it may do, how much budget it has left and whether it has paid.
Why do AI agents need economic firewalls?
Agents loop, retry, hand off work and call paid tools with no person approving each request. SatGate blocks what isn’t allowed before it runs. SatGate signs a receipt when it refuses an agent over a budget, a missing payment or a tool permission, and when an agent spends from a budget in Control.
Is an economic firewall the same as an API gateway?
No. An API gateway routes and secures traffic. An economic firewall adds per-agent permissions and budgets, tokens that can be narrowed for sub-agents, revokes, payment, and signed receipts for budget spends and for refusals over a budget, a missing payment or a tool permission.
How do I know whether I need an economic firewall?
When your agents can call paid models, APIs or MCP tools faster than a person can review what they do and spend. Start by listing which agents call what, then grade your setup with the readiness grader.
What is the first economic firewall control to implement?
Start with Observe: see which agent, route and tool is behind each request, without blocking anything. Then turn on Control for the risky routes, with budgets and revokes. Add Admit when you want external agents to pay.
SatGate checks every agent request before it runs
Put SatGate in front of your API or MCP tools. See every agent call, limit what agents can reach and spend, charge external agents where you choose, and keep signed receipts for budget spends and for refusals over a budget, a missing payment or a tool permission.