Built-in MCP Servers: Web Search, Documentation Query, and Code Search

What You'll Learn

✅ Understand the 3 built-in MCP servers and their use cases
✅ Know how to configure Exa Websearch API Key
✅ Learn to disable unnecessary MCP services
✅ Understand the architecture and working principles of the three-layer MCP system

Your Current Challenge

AI agents can only access local files and make network requests, but they lack professional search and documentation query capabilities. You want agents to be able to:

Search the web in real-time for the latest information
Consult official documentation for accurate API descriptions
Search GitHub repositories for implementation examples

But implementing these features manually adds development complexity.

When to Use This Approach

When you need to extend AI agent capabilities:

Scenario	Recommended MCP
Need to get the latest technical information, news, or industry trends	websearch (Exa)
Query official API documentation for libraries or frameworks	context7
Find implementation examples in GitHub repositories	grep_app (Grep.app)

Core Concepts: What is MCP?

MCP (Model Context Protocol) is a standard protocol that allows AI agents to access external tools and data sources. Simply put:

What is MCP?

MCP is like equipping an AI agent with a "toolbox" containing various professional tools (search, databases, APIs, etc.). Agents can call these tools on demand to access capabilities not available locally.

Oh-My-OpenCode provides a three-layer MCP system:

This lesson focuses on the first layer: built-in MCP servers.

Three Built-in MCP Servers

Oh-My-OpenCode includes 3 remote MCP servers that work out of the box (some require API Key configuration).

1. websearch (Exa AI)

Function: Real-time web search powered by Exa AI.

Use Cases:

Search for the latest technical articles and news
Find solutions to specific problems
Get industry trends and best practices

Configuration Requirements:

You need to set the EXA_API_KEY environment variable:

macOS/LinuxWindows

bash

export EXA_API_KEY="your-api-key-here"

powershell

setx EXA_API_KEY "your-api-key-here"

Getting Exa API Key

Visit Exa AI
Sign up for an account
Create an API Key in Dashboard
Add the Key to environment variables

Source Location: src/mcp/websearch.ts (lines 1-11)

2. context7

Function: Official documentation query, supporting any programming library or framework.

Use Cases:

Query API documentation for React, Vue, Next.js, etc.
Get official documentation for runtimes like Node.js, Python
Consult usage guides for open source projects

Configuration Requirements: No configuration required, works out of the box.

Source Location: src/mcp/context7.ts (lines 1-7)

3. grep_app (Grep.app)

Function: Ultra-fast GitHub code search for finding implementation examples.

Use Cases:

Find specific pattern implementations in open source projects
Learn how others write code
Find code snippets to solve specific problems

Configuration Requirements: No configuration required, works out of the box.

Source Location: src/mcp/grep-app.ts (lines 1-7)

Configuring and Disabling MCPs

Default Behavior

All built-in MCP servers are enabled by default. Oh-My-OpenCode automatically registers these services on startup.

Disabling Unnecessary MCPs

If certain MCP services are not needed, you can disable them in the configuration file:

jsonc

// ~/.config/opencode/oh-my-opencode.json or .opencode/oh-my-opencode.json
{
  "$schema": "./assets/oh-my-opencode.schema.json",

  // Disable unnecessary MCP servers
  "disabled_mcps": [
    "websearch",    // Disable web search (if you don't have Exa API Key)
    "grep_app"      // Disable GitHub code search
  ]
}

Why Disable MCPs?

Disabling unnecessary MCPs can:

Save resources: Reduce unnecessary connections and requests
Simplify configuration: Avoid prompts for unset API Keys
Improve stability: Reduce potential network failure points

Configuration Priority

The disable configuration priority for built-in MCPs:

Configuration Location	Priority
User config `~/.config/opencode/oh-my-opencode.json`	High (overrides project config)
Project config `.opencode/oh-my-opencode.json`	Medium
Code default	Low (all enabled)

How It Works: Remote MCP Configuration

All built-in MCP servers use remote (remote) mode, connecting to external services via HTTP/SSE protocol.

Configuration Mode (source code definition):

typescript

// src/mcp/websearch.ts
export const websearch = {
  type: "remote" as const,        // Fixed to "remote"
  url: "https://mcp.exa.ai/mcp?tools=web_search_exa",  // MCP server address
  enabled: true,                   // Enabled status (overridden by disabled_mcps)
  headers: process.env.EXA_API_KEY  // Optional request headers (API Key)
    ? { "x-api-key": process.env.EXA_API_KEY }
    : undefined,
  oauth: false as const,            // Disable OAuth auto-detection
}

Configuration Field Descriptions:

Field	Type	Description
`type`	`"remote"`	Fixed value, indicating remote MCP
`url`	`string`	HTTP address of the MCP server
`enabled`	`boolean`	Whether enabled (fixed as `true` in code, controlled by `disabled_mcps`)
`headers`	`object`	Optional HTTP request headers (for authentication)
`oauth`	`false`	Disable OAuth auto-detection (Exa uses API Key)

Common Pitfalls

Pitfall 1: websearch Requires API Key

Symptom: Agent fails when attempting to use websearch, prompting for missing API Key.

Solution:

bash

# Check if environment variable is set
echo $EXA_API_KEY

# If empty, set API Key
export EXA_API_KEY="your-actual-api-key"

# Or add permanently to shell config (~/.bashrc, ~/.zshrc, etc.)
echo 'export EXA_API_KEY="your-actual-api-key"' >> ~/.zshrc

Verify API Key

After setting, you can restart OpenCode or run diagnostic command to verify:

bash

oh-my-opencode doctor --verbose

Pitfall 2: MCP Still Prompted After Disabling

Symptom: Even after disabling an MCP, the agent still tries to use it.

Solution:

Check if configuration file path is correct:
- User config: ~/.config/opencode/oh-my-opencode.json
- Project config: .opencode/oh-my-opencode.json
Confirm JSON format is correct (note commas and quotes):

jsonc

{
  "disabled_mcps": ["websearch"]  // ✅ Correct
  // "disabled_mcps": ["websearch"],  // ❌ Error: no trailing comma allowed
}

Restart OpenCode for configuration to take effect.

Pitfall 3: Grep.app Results Inaccurate

Symptom: grep_app returns results that don't match expectations.

Possible Causes:

Search keywords too generic
Target repository inactive or deleted
Incorrect search syntax

Solution:

Use more specific search terms
Specify file type or language when searching
Visit Grep.app directly to manually verify

Summary

This lesson introduced Oh-My-OpenCode's 3 built-in MCP servers:

MCP	Function	Configuration Requirements	Main Use
websearch	Real-time web search	EXA_API_KEY	Get latest information
context7	Official documentation query	None	Consult API documentation
grep_app	GitHub code search	None	Find implementation examples

Key Takeaways:

Three-layer MCP System: Built-in → Claude Code Compatible → Skill Embedded
Enabled by Default: All built-in MCPs are enabled by default and can be disabled via disabled_mcps
Remote Mode: All built-in MCPs use HTTP/SSE protocol to connect to external services
Exa Requires Key: websearch requires the EXA_API_KEY environment variable

These MCP servers significantly expand AI agent capabilities, allowing them to access real-time information and professional knowledge bases.

Appendix: Source Code Reference

Click to expand source code locations

Updated: 2026-01-26

Function	File Path	Line Numbers
MCP factory function	`src/mcp/index.ts`	22-32
websearch configuration	`src/mcp/websearch.ts`	1-11
context7 configuration	`src/mcp/context7.ts`	1-7
grep_app configuration	`src/mcp/grep-app.ts`	1-7
McpNameSchema	`src/mcp/types.ts`	1-10
disabled_mcps field	`src/config/schema.ts`	331

Key Constants:

allBuiltinMcps: Built-in MCP configuration object, including websearch, context7, grep_app (src/mcp/index.ts:16-20)

Key Functions:

createBuiltinMcps(disabledMcps): Create list of enabled MCPs, filtering out disabled MCPs (src/mcp/index.ts:22-32)

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常见问题

Appendix

Changelog

Built-in MCP Servers: Web Search, Documentation Query, and Code Search

What You'll Learn

Your Current Challenge

When to Use This Approach

Core Concepts: What is MCP?

Three Built-in MCP Servers

1. websearch (Exa AI)

2. context7

3. grep_app (Grep.app)

Configuring and Disabling MCPs

Default Behavior

Disabling Unnecessary MCPs

Configuration Priority

How It Works: Remote MCP Configuration

Common Pitfalls

Pitfall 1: websearch Requires API Key

Pitfall 2: MCP Still Prompted After Disabling

Pitfall 3: Grep.app Results Inaccurate

Summary

Appendix: Source Code Reference

Built-in MCP Servers: Web Search, Documentation Query, and Code Search ​

What You'll Learn ​

Your Current Challenge ​

When to Use This Approach ​

Core Concepts: What is MCP? ​

Three Built-in MCP Servers ​

1. websearch (Exa AI) ​

2. context7 ​

3. grep_app (Grep.app) ​

Configuring and Disabling MCPs ​

Default Behavior ​

Disabling Unnecessary MCPs ​

Configuration Priority ​

How It Works: Remote MCP Configuration ​

Common Pitfalls ​

Pitfall 1: websearch Requires API Key ​

Pitfall 2: MCP Still Prompted After Disabling ​

Pitfall 3: Grep.app Results Inaccurate ​

Summary ​

Appendix: Source Code Reference ​

Built-in MCP Servers: Web Search, Documentation Query, and Code Search

What You'll Learn

Your Current Challenge

When to Use This Approach

Core Concepts: What is MCP?

Three Built-in MCP Servers

1. websearch (Exa AI)

2. context7

3. grep_app (Grep.app)

Configuring and Disabling MCPs

Default Behavior

Disabling Unnecessary MCPs

Configuration Priority

How It Works: Remote MCP Configuration

Common Pitfalls

Pitfall 1: websearch Requires API Key

Pitfall 2: MCP Still Prompted After Disabling

Pitfall 3: Grep.app Results Inaccurate

Summary

Appendix: Source Code Reference