A team is implementing MCP (Model Context Protocol) to expose internal tools to Claude agents. They need to expose a customer database query tool. What is the primary architectural benefit of MCP over custom tool definitions in the API request payload?

MCP's primary architectural benefit is standardization and reuse: tools are defined once on an MCP server and can be discovered and used by any MCP-compatible client (Claude agents, Claude desktop, third-party clients) without re-implementing tool schemas in each API call. This creates a separation between tool implementation (MCP server) and tool consumption (agents), enabling a shared tool ecosystem. Option A is incorrect — MCP tools don't execute faster; they're exposed over a protocol (stdio or HTTP) and go through the same API tool-calling mechanism. Option C invents an Anthropic requirement that doesn't exist; custom API tool definitions are fully supported and commonly used in production. Option B is incorrect — MCP does not provide automatic safety validation of tool outputs; that responsibility remains with the application layer.