Design Principles

These are rough guidelines to follow when shipping features for the MCP server. Apply them with nuance.

• Agent-Agnostic API: Use standards like MCP. Don't lock in to one LLM. Interoperability is key.
• Token-Optimized: Return semantic summaries. "LCP was 3.2s" is better than 50k lines of JSON. Files are the right location for large amounts of data.
• Small, Deterministic Blocks: Give agents composable tools (Click, Screenshot), not magic buttons.
• Self-Healing Errors: Return actionable errors that include context and potential fixes.
• Human-Agent Collaboration: Output must be readable by machines (structured) AND humans (summaries).
• Progressive Complexity: Tools should be simple by default (high-level actions) but offer advanced optional arguments for power users.
• Reference over Value: for heavy assets (screenshots, traces, videos), return a file path or resource URI, never the raw data stream. Some MCP clients support a built-in handling of heavy assets e.g. directly displaying images. This could be an exception.