# Registering a Server in a Host — Agent Frameworks and MCP Basics

Source: https://www.geekswithgeeks.com/en/agent-frameworks-mcp/cli-configure

> Add a local server to a desktop host and to Claude Code.

## A command and arguments

For a stdio server the host needs to know **how to start it**: a command and its arguments. Desktop hosts usually read this from a JSON config under a key named `mcpServers`. Claude Code can add one with `claude mcp add`. Restart the host after changing a config file.

## Register once, use everywhere

Each host has a way to register servers. After that, the model sees the tools like any others.

![Three steps: configure, connect, discover.](assets/figures/agent-frameworks-mcp/section-5-map.svg) — Figure 5.1 — Configure, connect and discover.

## Two ways to register

Use absolute paths in config files, because the host may start the process from a different working directory.

```json
// desktop host config (JSON)
{
  "mcpServers": {
    "calculator": {
      "command": "python",
      "args": ["/home/me/mcp/server.py"]
    }
  }
}

// Claude Code (shell)
// claude mcp add calculator -- python /home/me/mcp/server.py
```

## Fix "server not found" first

Most connection failures are a wrong path, a missing virtual environment or a command not on the host's PATH. Run the exact command in a terminal first; if it fails there, it will fail in the host.

**Quiz:** Why use absolute paths in a host config?

- [ ] Relative paths are illegal JSON
- [x] The host may launch the process from a different working directory
- [ ] Absolute paths are faster
- [ ] The model requires it

*Answer:* The host may launch the process from a different working directory. A relative path may not resolve from where the host starts the server.