feat(mcp): add grep_app builtin MCP for ultra-fast GitHub code search

- Add grep_app MCP configuration (https://mcp.grep.app)
- Update explore agent with grep_app usage guide:
  - Always launch 5+ grep_app calls with query variations
  - Always add 2+ other search tools for verification
  - grep_app is fast but potentially outdated, use as starting point only
- Update README.md and README.ko.md with grep_app documentation

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

README.ko.md

@@ -317,7 +317,10 @@ Syntax Highlighting, Autocomplete, Refactoring, Navigation, Analysis, 그리고
     - Use PascalCase for interface names
     - Use camelCase for function names
     ```
-- **Online**: 프로젝트 규칙이 전부는 아니겠죠. exa, context7 mcp 를 내장하여 검색 기능을 제공합니다.
+- **Online**: 프로젝트 규칙이 전부는 아니겠죠. 확장 기능을 위한 내장 MCP를 제공합니다:
+  - **context7**: 공식 문서 조회
+  - **websearch_exa**: 실시간 웹 검색
+  - **grep_app**: 공개 GitHub 저장소에서 초고속 코드 검색 (구현 예제 찾기에 최적)
 
 #### 멀티모달을 다 활용하면서, 토큰은 덜 쓰도록.
 
@@ -488,13 +491,17 @@ Google Gemini 모델을 위한 내장 Antigravity OAuth를 활성화합니다:
 
 ### MCPs
 
-기본적으로 Context7, Exa MCP 를 지원합니다.
+기본적으로 Context7, Exa, grep.app MCP 를 지원합니다.
+
+- **context7**: 라이브러리의 최신 공식 문서를 가져옵니다
+- **websearch_exa**: Exa AI 기반 실시간 웹 검색
+- **grep_app**: [grep.app](https://grep.app)을 통해 수백만 개의 공개 GitHub 저장소에서 초고속 코드 검색
 
 이것이 마음에 들지 않는다면, ~/.config/opencode/oh-my-opencode.json 혹은 .opencode/oh-my-opencode.json 의 `disabled_mcps` 를 사용하여 비활성화할 수 있습니다:
 
 ```json
 {
-  "disabled_mcps": ["context7", "websearch_exa"]
+  "disabled_mcps": ["context7", "websearch_exa", "grep_app"]
 }
 ```
 

README.md

@@ -314,7 +314,10 @@ Hand your best tools to your best colleagues. Now they can properly refactor, na
     - Use PascalCase for interface names
     - Use camelCase for function names
     ```
-- **Online**: Project rules aren't everything. Built-in exa and context7 MCP for web search.
+- **Online**: Project rules aren't everything. Built-in MCPs for extended capabilities:
+  - **context7**: Official documentation lookup
+  - **websearch_exa**: Real-time web search
+  - **grep_app**: Ultra-fast code search across public GitHub repos (great for finding implementation examples)
 
 #### Be Multimodal. Save Tokens.
 
@@ -485,13 +488,17 @@ Available agents: `oracle`, `librarian`, `explore`, `frontend-ui-ux-engineer`, `
 
 ### MCPs
 
-Context7 and Exa MCP enabled by default.
+Context7, Exa, and grep.app MCP enabled by default.
+
+- **context7**: Fetches up-to-date official documentation for libraries
+- **websearch_exa**: Real-time web search powered by Exa AI
+- **grep_app**: Ultra-fast code search across millions of public GitHub repositories via [grep.app](https://grep.app)
 
 Don't want them? Disable via `disabled_mcps` in `~/.config/opencode/oh-my-opencode.json` or `.opencode/oh-my-opencode.json`:
 
 ```json
 {
-  "disabled_mcps": ["context7", "websearch_exa"]
+  "disabled_mcps": ["context7", "websearch_exa", "grep_app"]
 }
 ```
 

src/agents/explore.ts

@@ -73,6 +73,46 @@ Your response has FAILED if:
 - **Using Git CLI extensively for repository insights**
 - **Using LSP tools for semantic code analysis**
 - **Using AST-grep for structural code pattern matching**
+- **Using grep_app (grep.app MCP) for ultra-fast initial code discovery**
+
+## grep_app - FAST STARTING POINT (USE FIRST!)
+
+**grep_app is your fastest weapon for initial code discovery.** It searches millions of public GitHub repositories instantly.
+
+### When to Use grep_app:
+- **ALWAYS start with grep_app** when searching for code patterns, library usage, or implementation examples
+- Use it to quickly find how others implement similar features
+- Great for discovering common patterns and best practices
+
+### CRITICAL WARNING:
+grep_app results may be **OUTDATED** or from **different library versions**. You MUST:
+1. Use grep_app results as a **starting point only**
+2. **Always launch 5+ grep_app calls in parallel** with different query variations
+3. **Always add 2+ other search tools** (Grep, ast_grep, context7, LSP, Git) for verification
+4. Never blindly trust grep_app results for API signatures or implementation details
+
+### MANDATORY: 5+ grep_app Calls + 2+ Other Tools in Parallel
+
+**grep_app is ultra-fast but potentially inaccurate.** To compensate, you MUST:
+- Launch **at least 5 grep_app calls** with different query variations (synonyms, different phrasings, related terms)
+- Launch **at least 2 other search tools** (local Grep, ast_grep, context7, LSP, Git) for cross-validation
+
+\`\`\`
+// REQUIRED parallel search pattern:
+// 5+ grep_app calls with query variations:
+- Tool 1: grep_app_searchGitHub(query: "useEffect cleanup", language: ["TypeScript"])
+- Tool 2: grep_app_searchGitHub(query: "useEffect return cleanup", language: ["TypeScript"])
+- Tool 3: grep_app_searchGitHub(query: "useEffect unmount", language: ["TSX"])
+- Tool 4: grep_app_searchGitHub(query: "cleanup function useEffect", language: ["TypeScript"])
+- Tool 5: grep_app_searchGitHub(query: "useEffect addEventListener removeEventListener", language: ["TypeScript"])
+
+// 2+ other tools for verification:
+- Tool 6: Grep("useEffect.*return") - Local codebase ground truth
+- Tool 7: context7_get-library-docs(libraryID: "/facebook/react", topic: "useEffect cleanup") - Official docs
+- Tool 8 (optional): ast_grep_search(pattern: "useEffect($$$)", lang: "tsx") - Structural search
+\`\`\`
+
+**Pattern**: Flood grep_app with query variations (5+) → verify with local/official sources (2+) → trust only cross-validated results.
 
 ## Git CLI - USE EXTENSIVELY
 

src/mcp/grep-app.ts

@@ -0,0 +1,5 @@
+export const grep_app = {
+  type: "remote" as const,
+  url: "https://mcp.grep.app",
+  enabled: true,
+}

src/mcp/index.ts

@@ -1,5 +1,6 @@
 import { websearch_exa } from "./websearch-exa"
 import { context7 } from "./context7"
+import { grep_app } from "./grep-app"
 import type { McpName } from "./types"
 
 export { McpNameSchema, type McpName } from "./types"
@@ -7,6 +8,7 @@ export { McpNameSchema, type McpName } from "./types"
 const allBuiltinMcps: Record<McpName, { type: "remote"; url: string; enabled: boolean }> = {
   websearch_exa,
   context7,
+  grep_app,
 }
 
 export function createBuiltinMcps(disabledMcps: McpName[] = []) {

src/mcp/types.ts

@@ -1,5 +1,5 @@
 import { z } from "zod"
 
-export const McpNameSchema = z.enum(["websearch_exa", "context7"])
+export const McpNameSchema = z.enum(["websearch_exa", "context7", "grep_app"])
 
 export type McpName = z.infer<typeof McpNameSchema>