Show HN: SatGate – Budget enforcement proxy for MCP tool calls (L402/macaroons) I built an open-source MCP proxy that enforces per-tool budgets on AI agent tool calls. The problem: MCP gives agents tool access with no economic controls. An agent stuck in a retry loop against a $0.10/call API burns real money until someone kills it. Auth says "who" and "what" — nothing says "how much." How it works: SatGate MCP Proxy sits between your agent and upstream MCP servers. Transparent relay — agents don't know it's there until they hit their budget.
Per-tool costs with wildcard matching (web_search: 5, gpt4_*: 25, dalle_generate: 50).Delegation: Parent agents can mint sub-agent tokens with carved budgets. Enforced cryptographically via macaroon HMAC chains — no DB lookup, microsecond verification.
Budget isolation is real — when research-agent hits 0, siblings and parent are unaffected.Two payment modes: - Fiat402: Credit-based budgets with delegation trees (enterprise) - L402: Lightning micropayments per tool call. Agent pays invoice, gets preimage, retries. Transport: stdio (local sidecar) or SSE/HTTP (remote, multi-agent). Written in Go. 28 tests. ~2,200 lines. GitHub: https://github.com/SatGate-io/satgate Blog: https://satgate.io/blog/beyond-connection-economic-governanc... |