Outbound MCP - Chatblocks

The outbound MCP connector lets you point Chatblocks at any Model Context Protocol server that speaks Streamable HTTP. List its tools, call one of them as the query for a block binding, and the platform refreshes on the usual cadence. This is how you wire blocks to Linear, GitHub, Notion, or any internal MCP server you’ve built — without writing a custom connector.

Outbound MCP data sources are a Builder beta feature. Free workspaces can read this page, but connector creation, connection tests, refreshes, and tool discovery return PRO_REQUIRED.

Add an MCP data source

Go to the wizard

/settings/data-sources/new/mcp.

Pick a label and the server URL

The URL must be HTTPS. Same SSRF rules as Postgres — scheme allowlist, hostname blocklist (localhost, *.local), literal-IP private-range matcher (including the ::ffff:hex IPv6 form).

Optionally paste a bearer token

Most third-party MCP servers require authentication. Paste the token; it’s stored in the encrypted credential blob.

Click Test Connection

The wizard runs a one-off connect + tools/list against the URL. On success, you see the discovered tools, so you can verify the surface before binding any blocks. The connection is closed immediately after.

Pick a cadence and save

Same cadence options as the other connectors: 5, 15, 60, 360, or 1440 minutes.

Connection model

The connector uses the official @modelcontextprotocol/sdk — the same SDK we use for inbound MCP. Transport is StreamableHTTPClientTransport with an optional bearer header. Each refresh creates a fresh client per request. Convex actions are short-lived; a long-lived MCP client would die between invocations. Refresh runs in a "use node" Convex action because the SSRF check imports node:dns/promises.

SSRF and DNS rebinding

Same two-layer defense as Postgres:

Sync check at add time and every refresh — HTTPS-only, hostname blocklist, literal-IP private-range matcher.
Async DNS re-resolve before every connect — dns.promises.lookup({ all: true }) rejects if any A/AAAA record falls in a private range. Defeats DNS rebinding.

A malicious server can’t trick the platform into connecting to your internal network even if it controls DNS.

Discover the tool surface

Two paths to see what’s available:

Test Connection in the wizard
dataSources.listMcpTools MCP read tool

The wizard’s Test Connection button returns the full tool list with descriptions. Useful before saving so you can copy a tool name into a binding.

Your agent can discover the surface programmatically through the inbound MCP server:

{
  "name": "dataSources.listMcpTools",
  "arguments": { "dataSourceId": "<mcp-data-source-id>" }
}

Returns the discovered tool list — agent-readable so it can build a binding without human help.

Bind a block

The query type is mcp.tool. The params carry the tool name, its arguments, and which field of the result to project from.

{
  "binding": {
    "dataSourceId": "<mcp-data-source-id>",
    "queryConfig": {
      "type": "mcp.tool",
      "params": {
        "tool": "linear.search_issues",
        "args": { "query": "is:open team:eng" },
        "projectionField": "issues"
      }
    },
    "projection": {
      "fields": {
        "label": { "literal": "Open eng issues" },
        "items": { "source": "issues", "format": "number" }
      }
    }
  }
}

projectionField tells the connector which field of the tool’s return object to hand off to the projection mapping. If the tool returns { issues: [...], cursor: "..." }, set projectionField: "issues".

Credential storage

The credential blob is JSON: { serverUrl, authToken? }. Encrypted via the workspace DEK (envelope encryption). Every decryption is audit-logged with the calling actor — same pattern as the other connectors.

What’s next

BYOK keys

Bring your own LLM key — used by scheduled runs that drive the agent loop.

Scheduled runs

Drive periodic agent loops over MCP — connect outbound MCPs and let your agent compose results.

​Add an MCP data source

​Connection model

​SSRF and DNS rebinding

​Discover the tool surface

​Bind a block

​Credential storage

​What’s next

BYOK keys

Scheduled runs

Add an MCP data source

Connection model

SSRF and DNS rebinding

Discover the tool surface

Bind a block

Credential storage

What’s next