MCP server

For every verified site, Sill runs a per-site Model Context Protocol (MCP) server at its edge, over Streamable-HTTP transport. MCP clients can connect to the site’s MCP endpoint to discover and invoke the site’s exposed skills.

Endpoint

POST https://edge.sill.so/v1/mcp/{site_key}

The transport is Streamable-HTTP, as defined in the MCP specification.

What it implements

initialize — the MCP handshake. Returns the server’s protocol version and capabilities.
tools/list — returns the site’s exposed skills as MCP tools. The tool set is backing-filtered — only skills the site actually exposes through a wired backing appear here (the same set the agent card advertises).
tools/call invocations are recorded in the site’s signed audit envelope.

Example — initialize

A minimal MCP initialize request, posted to a verified site’s MCP endpoint:

POST /v1/mcp/SITE_KEY HTTP/1.1
Host: edge.sill.so
Content-Type: application/json
Accept: application/json, text/event-stream

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": {
    "protocolVersion": "2025-03-26",
    "capabilities": {},
    "clientInfo": { "name": "example-client", "version": "0.0.0" }
  }
}

Replace SITE_KEY with the site key issued for the verified domain.

Skill execution

Connector-wired skills (e.g. catalog browse against a wired commerce backend) dispatch through Sill’s connector layer.
Skills without a wired backing fall back to discovery / observe-only.
Money-movement skills require a signed mandate and are gated to the Phase-2 transactional path. See the Transactional overview.

Scope of claim

MCP server responses are not signed. The signed surface is the agent card pointer to the MCP endpoint, not the MCP responses themselves. (See the agent card.)
The verified surface is live MCP discovery (initialize + tools/list) and the audited tools/call record. Full MCP skill execution is conditional on the skill’s backing and on Phase-2 gating for money-movement skills.