MCP server

You are wiring the Agentcard MCP server into this app's agent so it can act on
behalf of a connected user. We already store each user's connection
access_token + refresh_token from the connect flow.

ENDPOINT
POST https://mcp.agentcard.sh/mcp
  Authorization: Bearer <the user's connection access_token>
  Accept: application/json, text/event-stream
Standard MCP over Streamable HTTP: initialize -> notifications/initialized ->
tools/list -> tools/call, echoing the Mcp-Session-Id header. Use a
spec-compliant MCP client (e.g. @modelcontextprotocol/sdk with
StreamableHTTPClientTransport) — do not hand-roll the protocol.
The connection token IS the auth: do NOT configure OAuth on the MCP client and
never open the MCP server's hosted sign-in page in a browser. If a user ever
sees a "Connect your account" page at mcp.agentcard.sh, the client was wired
for OAuth discovery instead of the bearer token.

1. ONE CLIENT PER USER
Create the MCP client with that user's connection token. Never share a client
across users, and never expose the token outside your backend.

2. REGISTER TOOLS DYNAMICALLY
Register every tool tools/list returns instead of hardcoding names. Tools
Agentcard ships later then appear in the agent with zero code change.

3. HANDLE APPROVAL GATES
Sensitive tools (create_card, get_card_details) can return status
"approval_required" with an approval_id — nothing has happened yet. Resolve it
with approve_request. Auto-approve when the user just asked for the action;
confirm with them before revealing card credentials. NEVER write card numbers
or CVVs to logs, error reports, or analytics.

4. HANDLE EXPIRY
Connection tokens live 1 hour. On 401, refresh (with your PLATFORM access
token, not the connection token):
POST https://api.agentcard.sh/api/v2/connect/refresh
  Authorization: Bearer <platform access_token>
  { "refresh_token": "<stored>" }
-> new pair; replace BOTH stored tokens and reconnect the MCP client.

5. RELAY, DON'T FAIL
If a tool reports KYC or wallet funding is needed, relay the message to the
user and retry once they've completed it. A fresh connection listing zero
cards is expected — a token only sees the cards your app created for that
user.