Tools · Agent-integration primitives

ContextVM (CVM)

The Model Context Protocol carried over Nostr — tool servers addressed by public key instead of DNS or IP, with a pricing spec (CEP-8) that lets a server charge sats for the tool call itself.

What it is

ContextVM (CVM) carries the Model Context Protocol over Nostr. Instead of reaching a tool server at a domain or IP address, an agent reaches it by its Nostr public key; relays are the message bus. That takes API keys, inbound ports, TLS certificates, and DNS records out of the picture — a server publishes to and subscribes from relays rather than listening on a socket. Because it is built on MCP, tool schemas stay typed and the whole existing MCP surface still applies.

Its distinguishing addition is CEP-8, a capability-pricing and payment spec that lets an MCP server charge for a tool call itself — priced in sats, settled over Lightning (BOLT11 via NWC) or Cashu as the recommended rails. Where L402 gates an HTTP resource, CEP-8 gates the MCP invocation.

When to use it

• Exposing or consuming a paid MCP capability without DNS, TLS, API keys, or an inbound port.
• Addressing a tool server by identity (a keypair) rather than by location (a domain/IP).
• Publishing a capability’s schema and its price together as one signed, discoverable event (via CEP-6 announcements) rather than a listing plus out-of-band pricing.

Dependencies

A Nostr keypair for the server’s address, relay access for the transport, and — to charge or pay — an NWC connection string on each side (the server holds one to receive and verify settlement; the client holds one to pay). Built on MCP, so an MCP-capable client or SDK completes the picture.

Quick start

Build with the ContextVM TypeScript SDK (@contextvm/sdk) or the Rust SDK; the Gateway bridges an existing MCP server onto Nostr without rewriting it. Pricing rides the SDK’s payment API — the server declares its priced capabilities and wraps its transport with a payment processor; the client wraps its transport with the matching payment handler. Both sides take an NWC connection string. Discover live servers with the cvmi CLI. The protocol and the CEP series are documented at docs.contextvm.org.

Gotchas

• CEP-8 is a Draft spec — reference-implemented in the TypeScript SDK since v0.4.0, but still moving. Pin to a known SDK version.
• The ecosystem is small today — a handful of public servers and relays, against the wider MCP ecosystem’s tens of thousands of servers. With little to buy yet, the near-term use is on the serving side (exposing a paid tool), not the buying side.
• Relay availability is a liveness dependency — a server is only reachable through relays that carry its events. Publish to several (CEP-17 relay lists), the way you’d run more than one watchtower.
• Metadata leaks to relay operators — payloads can be encrypted (CEP-4), but which pubkey talks to which, and when, is visible to the relays carrying the traffic.
• A paid authorization grants execution, not a guaranteed result — if the response is lost in transit the spec does not require the server to replay it, and a retry may be charged again.