Too many tools: What GitHub learned about building for agents from their MCP Server launch

Sam Morrow and his team at GitHub developed the most-used remote MCP server in the world, despite initially building it as an internal side project. The server gained viral attention when it coincided with the launch of VS Code's Agent mode, leading to widespread adoption and challenges in user interaction. The team discovered that a granular approach to GitHub's API wasn't effective as agents struggled with too many tools, highlighting the need to design toolsets that match common workflow patterns. They emphasized the importance of semantic grouping, meaningful error messaging, and filtering tools based on authentication token scopes. Sam shared insights on designing MCP servers, advocating for prompt-first tool design, composable toolsets, and dynamic tool selection to enhance user and agent interactions. He also stressed the significance of annotations in MCP tools for better decision-making and user protection. The GitHub MCP server continues to evolve with community input, offering new features and encouraging engagement through forums and working groups.