How SaaS companies expose their API to AI agents with MCP

Your customers increasingly live inside AI assistants. They want to manage your product from Claude, pull data into Cursor, and drive it from their own agents — without switching tabs. Shipping an official MCP server is becoming the modern equivalent of publishing a public API: a distribution channel and a competitive necessity. This is the playbook for SaaS teams.

Why MCP matters for SaaS now

For a decade, the public API was how SaaS products extended their reach — integrations, automations, and ecosystems all grew from it. MCP is the next layer of that story. When a user can say "create a new project in our tool and assign it to me" directly inside their assistant, the product that has a working MCP server wins the moment. The one that doesn't gets skipped.

There's a land-grab dynamic too. Users tend to wire up one connector per job and leave it. Being the default MCP server in your category — the one that's reliable and well-scoped — is a durable advantage.

What to expose (and what not to)

Start with reads

The safest, highest-value first release is read-only: let agents fetch records, search, summarize, and report. This delivers immediate value with minimal risk and lets you learn how customers actually use the server.

Add writes deliberately

Creating and updating records is powerful but needs care. Roll these out tool by tool, and keep genuinely destructive operations (bulk deletes, billing changes) off by default or behind explicit configuration.

The hard part: auth and multi-tenancy

A SaaS MCP server has to authenticate each customer to their own data. There are two common patterns:

• Per-customer credentials — each customer supplies an API key or token scoped to their account, stored encrypted.
• OAuth — customers authorize through your existing OAuth flow, so access maps to their permissions automatically.

Either way, the credential lives on the server and is injected into upstream calls — the AI client only ever sees a URL. Cast supports bearer tokens, API keys, custom headers, and full OAuth (including Dynamic Client Registration) with all secrets encrypted at rest.

What customers get

Once live, customers connect with a snippet you can drop straight into your docs:

{
  "mcpServers": {
    "acme-app": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote@latest",
        "https://mcp.getcast.io/acme-app-cmpsaas7788"
      ]
    }
  }
}

A pragmatic rollout plan

• Week 1 — generate a server from your OpenAPI spec, expose read tools, test internally.
• Week 2 — wire per-tenant auth, add usage logging, run a private beta with a few customers.
• Week 3 — publish connect instructions in your docs, add selected write tools, announce.

Because Cast generates tools from your existing spec and hosts the endpoint, most of this timeline is product decisions — which tools, which auth — rather than infrastructure work.

Frequently asked questions