What is Model Context Protocol (MCP)?
One way to describe tools and data so any model client can find and call them.
Model Context Protocol (MCP) — The Model Context Protocol (MCP) is an open standard for connecting AI models to tools and data sources through a common interface, so one integration works across any model client that supports it. It replaces per-app plugins with a shared contract.
Why it matters
Before MCP, connecting a model to a piece of software usually meant writing a custom plugin for that one model's platform, then another for the next one. MCP fixes the shape of the problem: a server describes its tools once, and any client that speaks the protocol (Claude, ChatGPT, Cursor) can discover and call them the same way.
For a sales team, this means the CRM does not need a bespoke integration for every AI product a rep wants to use. One MCP server, built once, works with whichever client the team already has open. For an agency, it means client instances stay portable: the same tool contract works whether a client's team is on Claude or something else next year. What MCP does not do is decide who gets to call what, or what happens after a call is made; that is left to the server. SalesCrew's server currently publishes over 140 tools across contacts, deals, the inbox and cadences.
How MCP works, in outline
- 1
A server publishes its tools
It lists what it can do, such as create a contact or send a reply, with the arguments each needs.
- 2
A client connects
Claude, ChatGPT or another MCP client discovers the tool list over the connection.
- 3
A model decides to call one
Based on the user's request, the model picks a tool and fills in the arguments.
- 4
The server executes it
It runs the action against the real system and returns a result.
- 5
The model uses the result
It reports back to the user, or chains into another tool call.
The mistake to watch for
Questions
- How is MCP different from a REST API?
- A REST API is a specific interface one system exposes; a client has to learn its particular endpoints and shapes. MCP is a standard way of describing tools so that any compliant client can discover and call them without custom integration work per client. A server can implement MCP on top of a REST API it already has.
- Does using MCP make a system secure by default?
- No. MCP standardizes discovery and calling; it says nothing about who is allowed to call what. Permissions, rate limits, approval steps and audit logging all have to be built into the server that implements MCP.
- Which AI products can act as an MCP client?
- Claude (desktop and code), ChatGPT and Cursor all support MCP, along with custom agents built to speak the protocol. Any of them can connect to a compliant MCP server and call its tools.