Claude Code plugin¶

The LCP Claude Code plugin turns any pip-installed Python library into live, queryable documentation inside your agent session. Install it once from the Claude Code marketplace and Claude automatically knows how to look up functions, classes, signatures, and docstrings for every library your project uses — without pre-built manifests, without per-project setup.

What's included¶

When you install the plugin, Claude Code gets:

Component	What it does
MCP Server	`lcp serve-all` starts automatically on every session and exposes your Python environment's libraries as browsable MCP tools
`lcp-universal` skill	Teaches Claude to call `resolve_library()` before writing code that uses a third-party library — proactive, not reactive
`lcp-usage` skill	Guides Claude on when and how to use LCP tools for library research
`/lcp:resolve <pkg>`	Slash command: resolve a library and get a summary of its public API
`/lcp:scan <pkg>`	Slash command: scan a package and produce a structured module and symbol overview
Library explorer subagent	A read-only Claude Haiku subagent for deep API research; runs independently so it doesn't consume your session's context
Session hook	Warns immediately at session start if `lcp` is not on `PATH`, instead of failing silently
Registry support	Optional `userConfig.registries` field for connecting to a private or team registry with pre-built manifests

Installation¶

Prerequisites¶

Claude Code installed
lcp installed and available on your PATH:

pip install lcp
lcp --version

Install from the marketplace¶

The plugin is published to the Claude Code marketplace under the zazza123/lcp namespace. Add the marketplace and install the plugin in two commands:

/plugin marketplace add zazza123/lcp
/plugin install lcp@lcp

That's it. Claude Code reads the plugin manifest, registers the MCP server, the skills, the commands, and the subagent. Open a new session and the server starts automatically.

Configuring a private registry at install time

During plugin install, you can set the registries option to point to a team registry:

/plugin install lcp@lcp registries="https://your-registry.example.com"

Alternative: local directory¶

If you have a local clone of the repository and want to load the plugin directly — for example when developing the plugin itself:

claude --plugin-dir /path/to/lcp/plugin/lcp

Alternative: MCP-only (Cursor, Claude Desktop)¶

If you only need the MCP server without skills, hooks, or commands, add the server directly to your client's MCP config:

Claude CodeCursor / Claude Desktop

claude mcp add lcp -- lcp serve-all

Add to .cursor/mcp.json or claude_desktop_config.json:

{
  "mcpServers": {
    "lcp": {
      "command": "lcp",
      "args": ["serve-all"]
    }
  }
}

How it works¶

Once the plugin is active, the typical interaction looks like this:

User: "Set up FastAPI routes with proper dependency injection"

Claude:
  1. resolve_library("fastapi")                → scanned + cached
  2. list_modules()                            → finds fastapi.routing
  3. list_symbols(module="fastapi.routing")    → finds APIRouter, Depends
  4. get_symbol("fastapi.routing:APIRouter")   → full signature
  5. get_class_members("fastapi:Depends")      → understands dependencies
  6. Writes accurate, idiomatic code

The lcp-universal skill drives this flow automatically: whenever Claude detects that a task involves an external Python library, it calls resolve_library("package") first. The MCP server checks ~/.lcp/cache/ for a cached manifest; if none is found, it scans the pip-installed package on the fly and caches the result. Subsequent calls to the same library in the same session are instant.

The skills, commands, and subagent are guidance and convenience layers on top of the MCP server — they don't change what the server does, they change how Claude uses it.

Configuring a private registry¶

By default, lcp serve-all resolves libraries from your local Python environment. If your team maintains a private registry with pre-built manifests for internal packages, configure the plugin to use it:

claude plugin config lcp registries "https://your-registry.example.com"

Multiple registries can be listed comma-separated; only the first is used as the active registry. The option maps to the --registry flag passed to lcp serve-all at startup.

Troubleshooting¶

lcp command not found

Both the session hook and the startup wrapper check for lcp on PATH. Install it with pip install lcp and confirm lcp --version works in the same shell environment Claude Code uses.

MCP server not starting

Run lcp serve-all manually in your terminal to check for errors. On Unix systems, bin/serve.sh must be executable — run chmod +x plugin/lcp/bin/serve.sh if needed. Confirm Claude Code shows lcp in its active MCP servers list.

Library not resolving

The package must be pip-installed in the Python environment lcp uses. Run lcp scan <package> manually to verify the library can be introspected. If scanning succeeds but the MCP tool still fails, restart the Claude Code session to reload the server.