MCP (Model Context Protocol) vs Native Function Calling Comparison

// Claude Code — adding a remote HTTP MCP server to .mcp.json
// Source: code.claude.com/docs/en/mcp (remote HTTP is the recommended transport)
{
  "mcpServers": {
    "internal-docs": {
      "type": "http",
      "url": "https://mcp.example-internal.com/v1",
      "headers": {
        "Authorization": "Bearer ${MCP_API_TOKEN}"
      }
    }
  }
}

// managed-settings.json — org-wide rollout + policy
// Both keys are TOP-LEVEL, NOT under "permissions".
// managedMcpServers: CHANGELOG v2.1.259 — "same entry format as .mcp.json";
// entries that run a command (stdio/local) are skipped.
{
  "managedMcpServers": {
    "internal-docs": {
      "type": "http",
      "url": "https://mcp.example-internal.com/v1"
    }
  },
  "deniedMcpServers": [
    { "serverUrl": "https://*.untrusted.example.com/*" }
  ]
}
// deniedMcpServers entries are single-key OBJECTS (serverUrl | serverCommand |
// serverName). serverName does not expand wildcards — use serverUrl to enforce.

// Anthropic Messages API - native tool use (function calling)
// Source: platform.claude.com/docs/en/agents-and-tools/tool-use/overview
{
  "model": "claude-sonnet-5",
  "max_tokens": 1024,
  "tools": [
    {
      "name": "get_weather",
      "description": "Returns the current weather for the given city",
      "input_schema": {
        "type": "object",
        "properties": {
          "location": { "type": "string", "description": "City name, e.g. Istanbul" }
        },
        "required": ["location"]
      }
    }
  ],
  "messages": [
    { "role": "user", "content": "What's the weather in Istanbul?" }
  ]
}

// The model returns a tool_use block, the application code runs it,
// and the result is sent back as tool_result in a second request.
// This requires two full API round-trips (no separate server process).