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.
Looking for the other direction — Catalyst's own management tools inside your AI coding assistant? That is the Catalyst MCP server, hosted by Diagrid, and unrelated to the project resources described here.
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 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 API token
- Filters tool discovery (
tools/list) down to the tools the caller is allowed to use - Rejects unauthorized tool calls (
tools/call) with403before 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. |
| Response caching | An opt-in TTL cache at the sidecar that serves repeated tool calls from memory. See Response caching. |
