Obol: free self-hosted MCP gateway with argument-level Cedar policies
ToBeContinuedHermit · reddit · 2026-10-03
The author details the free self-hosted release of Obol, a gateway whose headline feature is argument-level tool policy — instead of deciding whether an agent may call createrefund, Cedar policies (default-deny, evaluated in-process) express conditions like "refunds up to $100":
- tools/list only exposes tools the key can actually call
- Destructive prod tools require approval; approved calls run once against an idempotency record, so retrying agents can't double-refund
- Every call gets a receipt with the deciding policy, upstream id, vendor status and an evidence class; federated/third-party MCP routes are labeled unverified
- Vendor credentials live in a vault, decrypted only on the outbound hop
- Bring-your-own tools via remote MCP or OpenAPI import, plus 100+ reviewed native connectors
- Model calls share the same key: OpenAI-compatible /v1 with pre-dispatch per-key budgets
Single Docker Compose deploy, free with no quota; closed source, single host only.
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