Ucn MCP server

UCN - Universal Code Navigator

See what code does before you touch it.

If you work with AI Agents, add UCN as a Skill or MCP tool. One tool gives the agent compact, source-linked answers to caller, impact, and test questions, with uncertainty labeled instead of guessed.

Conceptual overview · Still image

Use the CLI directly, install the agent skill, or connect through MCP. One engine supplies all three:

Terminal              AI Agents           Agent Skills
       │                    │                    │
      CLI                  MCP                 Skill
       └────────────────────┼────────────────────┘
                            │
                     ┌──────┴──────┐
                     │ UCN Engine  │
                     │  commands   │
                     │ tree-sitter │
                     └─────────────┘

UCN uses tree-sitter abstract syntax trees (ASTs) for static code analysis, without compiling the project or starting a language server. The CLI runs on demand and reuses an incremental index; MCP keeps a process available for repeated queries. No project configuration is required, and the cache lives outside the repository.

Supports JavaScript, TypeScript, JSX/TSX, Python, Go, Rust, Java, C, C++, C#, and HTML inline scripts.

Install

npm install -g ucn                    # Node.js 20+

In the shell

From a project directory:

ucn repo
ucn show handleRequest --lines
ucn source handleRequest --raw
ucn impact --staged --lines
ucn check --staged

repo maps the project. show --lines locates callers, source --raw retrieves the implementation, and impact and check inspect a staged change. When a name is ambiguous, find returns a file:line:name handle that subsequent commands accept.

--lines returns path:line:text records; --raw returns source code. Both fit an agent's existing scripts without parsing a human-readable report.

Text search remains useful for comments, configuration, strings, and code outside the supported languages. usages provides the literal-name inventory when the task needs every occurrence, including those that are not calls.

Code navigation and change analysis

show gathers a symbol's signature, source, callers, callees, and related context. Select the sections you need or set an output budget to keep the answer focused. trace follows the call graph across files, down into callees or up through callers toward entry points. Unverified relationships remain visible, and the tree's accounting reports where exploration stopped.

impact connects a symbol or Git diff to its callers. tests follows indexed call and reference paths to identify statically linked tests, including links several hops away. plan previews a rename or signature change with source locations and review items; it does not edit files. Together these commands support code exploration, refactoring, and change review from a terminal or an AI agent.

What an answer establishes

Shortened. The full README is on GitHub.