MCP (Model Context Protocol)
The Model Context Protocol (MCP) lets a Callable agent securely connect to external tools, APIs, databases, CRMs, calendars, and automation platforms through one standard interface — so the agent can do things, not just talk about them.
Think of MCP as USB-C for AI. Instead of building a separate integration for every service, your agent speaks one common protocol and can reach anything that exposes an MCP server.
Why it matters
Without a tool layer, an agent can only chat:
With MCP connected, the same request becomes a real action:
The agent goes from a conversational assistant to a digital worker that completes tasks.
How it works
Caller → Callable agent → MCP client → MCP server → your external service → response back to the callerThe agent never talks to Google Calendar, Stripe, or your CRM directly. It talks to an MCP server, which lists the tools it offers and securely runs each request. At connect time Callable performs the MCP handshake (initialize → tools/list), and each remote tool becomes a function the agent can call mid-conversation — on both voice calls and web chat.
What an MCP server exposes
Typical tools an MCP server might offer: check calendar, create appointment, search a customer, update a CRM record, send email / SMS / WhatsApp, create an invoice, process a payment, open a support ticket, query a database, search files, or run a custom API request. The agent discovers these automatically and decides when to use them based on what the caller asks.
What you can connect
Virtually anything that exposes an MCP server — for example Google Calendar / Gmail / Drive / Sheets, Outlook & Microsoft 365, Notion, Slack, HubSpot, Salesforce, Pipedrive, Stripe, Twilio, WhatsApp Business, Shopify, PostgreSQL / MySQL / MongoDB, Supabase, Firebase, Zapier, n8n, Airtable, GitHub, and your own internal REST APIs.
Add an MCP server in Callable
- Open your agent → MCPs (on the Settings tab, and in the builder's MCP section).
- Click Add MCP and fill in:
- Name — a label for the server.
- URL — the MCP server's endpoint.
- Timeout (ms) — how long to wait per request (default 10000).
- Headers — key/value pairs sent on every request (e.g. an
Authorizationtoken for auth). - Query parameters — appended to the URL.
- Save. Callable connects to the server, discovers its tools, and the agent can start using them on the next call or chat.
Why MCP beats one-off integrations
Every traditional integration is built and maintained separately — different auth, docs, and code for each API. MCP replaces all of that with a single protocol: connect once, and the agent gains every tool that server exposes. That means faster setup, easier maintenance, secure authentication, automatic tool discovery, and unlimited room to grow.