webmcp

<essential_principles>

WebMCP is a browser-native standard that exposes structured tools for AI agents on websites. Instead of screen-scraping, agents interact through typed JavaScript APIs and HTML annotations.

Two APIs:

• Imperative API — window.navigator.modelContext — register tools via JavaScript
• Declarative API — HTML toolname/tooldescription attributes on <form> elements

Prerequisites: Chrome 146.0.7672.0+, chrome://flags/#enable-webmcp-testing enabled.

Core principles that always apply:

1. Tools must be atomic and composable — one function per tool, no overlapping tools with nuanced differences. Combine similar tools into one with input parameters.

2. Accept raw user input — tools should accept natural strings (e.g., "11:00") not computed values (e.g., minutes-from-midnight). Minimize cognitive computing for the model.

3. Validate in code, not schema — schema constraints are helpful but not guaranteed. Validate within execute functions and return descriptive errors so agents can self-correct.

4. Update UI before returning — agents use UI state to verify execution. Ensure execute/submit logic updates visible state before resolving.