MCP AST Explorer

io.github.LovRanRanPublished by GitHub account LovRanRanv0.1.0Updated Oct 24, 2026

Python symbol exploration for codebase onboarding agents.

VerifiedSTDIODesktop onlyKnowledge & MemoryDeveloper Tools

Overview

AI-generated overview

A local MCP server that indexes Python source with LibCST and lets an assistant look up definitions, signatures, references, callers and subclasses.

What you can do
Find definitions of modules, classes, functions and methods in a Python file, and return their signatures and same-module name references. Trace direct callers of a function or method and list direct subclasses of a class. Report structured not-found or unsupported-language results instead of guessing. Answer a health check for smoke testing.
When to use it
Useful when an assistant is onboarding onto a Python codebase and needs symbol-grounded answers about where things are defined, how they are called, or what inherits from what. It is a good fit alongside repository-mapping and test-running servers in a codebase onboarding workflow.
Requirements
Runs as a local stdio process installed from the PyPI package mcp-ast-explorer, with uv used in the documented setup. It parses Python files only; no accounts, API keys or environment variables are declared.
Before you install
Python-only v1: TypeScript is a placeholder and not implemented. Cross-file imports, aliases, star imports, qualified references and dynamic attribute access are not resolved, and call chains and class hierarchies return direct relationships only, so results can be incomplete. It reads local source files, so point it only at code you are comfortable exposing to the assistant.

Installation

In SourceWeft

  1. Open MCP AST Explorer in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

mcp-ast-explorer

MCP server for deterministic Python codebase symbol exploration.

mcp-ast-explorer indexes Python source files with LibCST and exposes focused MCP tools for codebase onboarding: definition lookup, function signatures, local references, direct call chains, and simple class hierarchy queries.

Codebase Onboarding Stack

mcp-ast-explorer is the semantic symbol layer in a three-server MCP tool stack for Project 6 wayfinder, a codebase onboarding agent.

  • mcp-repo-mapper maps repository structure, languages, entry points, framework evidence, and Python dependency edges.
  • mcp-ast-explorer provides symbol-grounded Python definition, signature, reference, call-chain, and class-hierarchy lookups.
  • mcp-test-runner runs local pytest/Jest checks and coverage summaries so agent claims can be verified against execution.

In wayfinder, this server feeds entry-point and symbol explanation while refusing to invent missing symbols.

Status

This is a Python-only v1. TypeScript is registered as an unsupported backend placeholder so the server has an explicit extension point, but TypeScript analysis is not implemented yet.

The server does not use an LLM for symbol lookup. If a requested symbol or class is not present in the parsed index, tools return a structured not-found result instead of inventing an answer.

Tools

ToolPurpose
health()Returns ok for smoke checks.
find_definition(path, symbol, language="python")Finds a module, class, function, or method definition.
function_signature(path, symbol, language="python")Returns the signature for a function or method symbol.
find_references(path, symbol, language="python")Returns same-module CST name references for an existing symbol.
call_chain(path, from_symbol, depth=2, language="python")Returns direct callers detected from local references.
class_hierarchy(path, class_name, language="python")Returns direct subclasses detected from simple base-class names.

Supported Scope

  • Python files parsed by LibCST.
  • Symbol kinds: modules, classes, functions, and methods.
  • Same-module reference lookup for simple names.
  • Direct caller detection from function or method containers.
  • Direct subclass detection for simple class Child(Base): inheritance.
  • Structured error responses for unsupported languages and missing symbols.

Current Limitations

  • Cross-file imports and package-wide resolution are out of scope for v1.
  • Aliases, star imports, dynamic attribute access, and qualified references are not resolved.
  • call_chain currently returns direct callers only; recursive multi-hop expansion is not implemented.
  • class_hierarchy currently returns direct subclasses only and handles simple base names.
  • TypeScript is intentionally unsupported in v1.

Local Development

Install dependencies:

bash
uv sync --extra dev

Run the MCP server:

bash
uv run mcp-ast-explorer

Run verification:

bash
uv run ruff check .uv run mypyuv run pytest

License

MIT

Source: README.md at commit 8126b9f

Tools

0
SourceWeft has not started this package in its sandbox yet, so its tools are not known.

Version history

1
  1. v0.1.0LatestSep 16, 2026

Score

50% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 days25 pts

    Keep the endpoint answering the MCP handshake; SourceWeft probes it every 30 days.

  • Auth declared10 pts

    Declare the credential headers in the registry entry, or keep the endpoint answering the probe so its auth can be classified.

  • Tools listed15 pts

    Answer tools/list without a credential, or ship a package that starts in a sandbox without one.

  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts