MCP on Catalyst

Catalyst puts a proxy endpoint in front of every Model Context Protocol (MCP) server your agents use. Your agent points its existing MCP client at one Catalyst URL; Catalyst forwards the call to the real upstream server, injects the upstream credentials, and enforces a per-tool access policy on the way through.

Because the proxy endpoint speaks plain MCP over HTTP, off-the-shelf MCP clients and agent frameworks work unchanged — there is no Catalyst-specific MCP SDK to adopt. The agent only ever sees the Catalyst endpoint and a token; it never holds the upstream server's URL or credentials.

How it works

You register an upstream MCP server once as an MCPServer connection — from the MCP Catalog or your own URL. Catalyst exposes it on your project's HTTP endpoint at a stable path keyed by the connection name:

https://<project-http-endpoint>/v1.0/diagrid/mcp/<mcp-server-name>

The agent (the MCP client) connects to that URL and authenticates with its App ID's API token in the dapr-api-token header. Catalyst resolves the connection, applies the access policy attached to it, and — if the call is allowed — forwards it to the upstream server with the configured upstream credentials attached.

For each call, Catalyst:

• Authenticates the caller by its App ID API token
• Filters tool discovery (tools/list) down to the tools the caller is allowed to use
• Rejects unauthorized tool calls (tools/call) with 403 before they reach the server
• Injects the upstream server's credentials so they never live in agent code
• Captures logs, metrics, and traces for the call

What you control

Concern	How
Which upstream server	An MCPServer connection — enabled from the catalog or declared with your own URL and transport.
Who can call which tools	An MCPServerAccessPolicy — a deny-by-default, per-tool, per-caller allow-list managed with diagrid mcpserver access.
Upstream credentials	Configured on the MCPServer (static headers, OAuth 2.0, or SPIFFE) and stored in your project's secret store. See Authentication.

Get started

Connect an MCP client

Point a standard MCP client at Catalyst's MCP proxy endpoint and discover tools.

Add an MCP server

Enable a catalog entry or register your own MCP server connection.

Control tool access

Grant and revoke per-tool, per-caller access with a deny-by-default policy.

Authentication

Authenticate the client to Catalyst and Catalyst to the upstream MCP server.