MCP CLI: Dynamic discovering and interacting with MCP servers

Instead of loading all tool definition upfront (static context), mcp-cli allows the agent to pull in only the information they need, when they need it.

Step 1: "What servers exist?" → mcp-cli Step 2: "What are the params for tool X?" → mcp-cli github/search Step 3: Execute → mcp-cli github/search '{"path": "README.md"}'