How does opencode implement web search?

how does open code implements web search?

OpenCode implements web search primarily through its websearch and codesearch tools, which leverage Exa AI's hosted Model Context Protocol (MCP) service.

###Core Implementation

The implementation is found in packages/opencode/src/tool/websearch.ts and packages/opencode/src/tool/codesearch.ts.

####1. Web Search Tool (websearch)

This tool performs broad web searches. It works by sending a JSON-RPC request to Exa's hosted MCP endpoint:

• Endpoint: https://mcp.exa.ai/mcp
• Method: tools/call
• Tool Name: web_search_exa
• Parameters: It supports parameters like query, numResults, livecrawl (cached vs. live), and type (auto, fast, deep).

The tool processes the response as a Server-Sent Events (SSE) stream, specifically looking for data: lines that contain the search results in Markdown format.

####2. Code Search Tool (codesearch)

Similar to websearch, but optimized for finding technical documentation, API examples, and library usage.

• Tool Name: get_code_context_exa
• Parameters: Includes a tokensNum parameter (default 5000) to control the amount of context returned.

###Enabling Web Search

According to packages/opencode/src/tool/registry.ts, these tools are not active for all providers by default. They are enabled if:

1. The model provider is opencode (OpenCode Zen).
2. OR the environment variable OPENCODE_ENABLE_EXA is set to true or 1.
3. OR experimental flags like OPENCODE_EXPERIMENTAL or OPENCODE_EXPERIMENTAL_EXA are active.

###Comparison with webfetch

OpenCode also includes a webfetch tool (packages/opencode/src/tool/webfetch.ts). While websearch is for discovery (finding information), webfetch is for retrieval (reading a specific URL). webfetch fetches raw HTML/text and converts it to Markdown using turndown.

###Permissions

Both tools are subject to OpenCode's permission system. Before execution, they trigger a permission check (e.g., permission: "websearch") to ensure the user has authorized the tool to perform searches.

how does codesearch works exactly?

The codesearch tool is a specialized tool for finding programming-related context (APIs, libraries, SDKs, and code patterns). It is implemented as a client for Exa AI's hosted Model Context Protocol (MCP) service.

Here is exactly how it works under the hood:

###1. Configuration and Availability

The tool is defined in packages/opencode/src/tool/codesearch.ts. It is only enabled if:

• You are using the OpenCode Zen provider (opencode).
• OR the environment variable OPENCODE_ENABLE_EXA is set to true or 1.

###2. Parameters

It accepts two parameters:

• query: A string describing the programming concept or problem (e.g., "React useState hook examples").
• tokensNum: An integer between 1000 and 50000 (default: 5000). This controls how much context (code snippets, documentation) is returned.

###3. Permission Check

Before execution, the tool calls ctx.ask to verify permissions. It uses the codesearch permission key. If your opencode.json has "codesearch": "ask", you will be prompted to approve the specific query.

###4. Communication Protocol (MCP over HTTP)

Instead of a standard REST API, it uses the Model Context Protocol (MCP) via JSON-RPC 2.0 over HTTP:

• Endpoint: https://mcp.exa.ai/mcp
• Method: POST
• Headers: It requests application/json and text/event-stream.
• Authentication: Notably, no API key is required. The tool connects to Exa's public/hosted MCP bridge directly.

###5. Request Payload

The tool constructs a JSON-RPC request to call the remote get_code_context_exa tool:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "get_code_context_exa",
    "arguments": {
      "query": "<your_query>",
      "tokensNum": 5000
    }
  }
}

###6. Streaming Response (SSE)

Exa returns the results as a Server-Sent Events (SSE) stream. The implementation:

1. Waits for lines starting with data: .
2. Parses the JSON data in those lines.
3. Looks for result.content, which contains an array of results.
4. Returns the text from the first content item as the tool's output.

###7. Execution Safeguards

• Timeout: The request has a 30-second timeout (abortAfterAny(30000, ...)).
• Error Handling: If the search fails or returns no results, it provides a descriptive error message suggesting the user be more specific about the library or framework.

###Comparison: codesearch vs websearch

While both use the same Exa MCP endpoint, they call different internal Exa tools:

• websearch calls web_search_exa (optimized for general web discovery).
• codesearch calls get_code_context_exa (optimized for extracting high-token-count code documentation and snippets).