docs: websearch tool (#12359)

Author: ariane-emory

packages/web/src/content/docs/tools.mdx

@@ -286,6 +286,39 @@ Allows the LLM to fetch and read web pages. Useful for looking up documentation
 
 ---
 
+### websearch
+
+Search the web for information.
+
+:::note
+This tool is only available when using the OpenCode provider or when the `OPENCODE_ENABLE_EXA` environment variable is set to any truthy value (e.g., `true` or `1`).
+
+To enable when launching OpenCode:
+
+```bash
+OPENCODE_ENABLE_EXA=1 opencode
+```
+:::
+
+```json title="opencode.json" {4}
+{
+  "$schema": "https://opencode.ai/config.json",
+  "permission": {
+    "websearch": "allow"
+  }
+}
+```
+
+Performs web searches using Exa AI to find relevant information online. Useful for researching topics, finding current events, or gathering information beyond the training data cutoff.
+
+No API key is required — the tool connects directly to Exa AI's hosted MCP service without authentication.
+
+:::tip
+Use `websearch` when you need to find information (discovery), and `webfetch` when you need to retrieve content from a specific URL (retrieval).
+:::
+
+---
+
 ### question
 
 Ask the user questions during execution.