Model Context Protocol (MCP)
One-line definition: An open protocol that defines how AI applications connect to external tools and information sources. Access still depends on the host, server, and configured permissions.
Quick Take
- In brief: MCP defines a common way for AI applications to connect to tools and data.
- Useful for: Connecting an AI client to external services through a shared interface.
- Main limit: The protocol does not make a server safe or a tool call authorized.
Overview
MCP is an open protocol that connects an AI application to external tools and information sources. A client and server can exchange requests through a host application. What the application can access depends on its configuration and permissions.
Core Definition
Formal Definition
The Model Context Protocol (MCP) defines how a host application, its client connection, and an MCP server communicate. Servers can expose capabilities such as tools, resources, and prompts. The protocol does not itself grant access to a user’s files or systems.
Background and Evolution
Background
Before MCP, each application often needed a separate integration for each tool or data source. MCP provides a shared protocol for these connections.
Development
Anthropic introduced MCP in 2024. The specification has since evolved. Optional extensions and newer features require support from the client and server; compatible support is not automatic.
How It Works
- The host application starts or connects to an MCP client.
- The client connects to an MCP server and negotiates supported capabilities.
- The server lists tools or provides resources that it has been configured to expose.
- The host decides what to show the model and whether a tool call needs user approval.
A connection does not make every available action safe. The host and server still need access controls.
Applications in Software Development and Testing
- Test reports: A server can provide a tool that reads a test run or retrieves a report.
- Repository information: A server can expose selected files, issue data, or build results.
- Controlled actions: A server can start a permitted workflow. Use approval and logging for changes that affect shared systems.
Strengths and Limitations
Strengths
- Reusable integration: A shared protocol can reduce custom connection code.
- Discoverable capabilities: Clients can learn which tools or resources a server offers.
Limitations and Risks
- Partial support: Clients and servers may implement different features or protocol versions.
- Permission risk: A server may expose sensitive data or actions. Apply least privilege and inspect tool behavior.
- No automatic freshness: Data freshness depends on the connected source and server implementation.
Comparison with Similar Terms
| Term | Main role |
|---|---|
| MCP | Connects an AI application to tools and context providers |
| Function calling | Lets a model request a tool through a particular model API |
| REST API | Lets software exchange requests with a web service |
MCP can carry tool interactions, but it does not replace the APIs that the server uses behind the connection.
Best Practices
- Start with read-only access and add write access only when needed.
- Review server identity, available tools, and required permissions.
- Require confirmation for destructive or externally visible actions.
- Log tool calls and test failure handling.
- Check client and server support before relying on an optional feature.
Common Pitfalls
- Treating MCP as a security boundary: The protocol does not enforce every host or server permission.
- Assuming “write once, run everywhere”: Implementations support different features and policies.
- Assuming current data: The connected service may cache or delay updates.
FAQ
What can a team do with MCP in software testing?
A team can connect a client to a server that exposes a test-report lookup tool. The server should limit which reports the tool can access.
Does MCP make a tool call safe?
No. The host and server must control access, validate inputs, and provide approval where needed. Review the actual operation before enabling it.