pharo-smalltalk-interop-mcp-server: Instructions file for Claude Code

CLAUDE.md

pharo-smalltalk-interop-mcp-server CLAUDE.md is an instructions file for Claude Code from mumez/pharo-smalltalk-interop-mcp-server. It costs 2,406 tokens per session, scanned A, original, MIT.

A Python server that lets coding agents communicate with local Pharo Smalltalk environments, which are running workspaces for Smalltalk code.

In plain words
What is it for?
It helps evaluate Smalltalk code, find classes and methods, inspect source, manage packages, install projects, run tests, and inspect Pharo user interfaces.
Why use it?
It gives an agent one interface for inspecting, changing, testing, and debugging Pharo projects instead of handling each task manually.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions CLAUDE.md; mentions Claude Code.

This is mumez/pharo-smalltalk-interop-mcp-server's own configuration. It tells Claude Code how to work on pharo-smalltalk-interop-mcp-server itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything pharo-smalltalk-interop-mcp-server configures →

Reuse

Borrowing it

Nothing to install: this file belongs to mumez/pharo-smalltalk-interop-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/mumez/pharo-smalltalk-interop-mcp-server/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/mumez/pharo-smalltalk-interop-mcp-server

Made for: Claude Code.

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Per session 2,406 This file is loaded in full into every session.
When invoked 2,406 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.02406 $0.02406
Opus 5 $0.01203 $0.01203
Sonnet 5 $0.00481 $0.00481
Haiku 4.5 $0.00241 $0.00241

Measured 10d ago against content hash 0fe3bf24aae4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

pharo-smalltalk-interop-mcp-server CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 331 lines

How it starts

The opening of the file, as written. The whole thing — 331 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

This is a Python-based MCP (Model Context Protocol) server designed to communicate with local Pharo Smalltalk images. The server provides an interface for:

  • Code Evaluation: Execute Smalltalk expressions and return results
  • Code Introspection: Retrieve source code, comments, and metadata for classes and methods
  • Search & Discovery: Find classes, traits, methods, references, and implementors
  • Package Management: Export and import packages in Tonel format
  • Project Installation: Install projects using Metacello
  • Test Execution: Run test suites at package or class level
  • UI Debugging: Capture screenshots and inspect UI structure for World morphs, Spec presenters, and Roassal visualizations

Development Setup

This project uses uv as the Python package manager. Prerequisites:

Environment Variables

You can configure the server using environment variables:

  • PHARO_SIS_PORT: Port number for PharoSmalltalkInteropServer (default: 8086)

Common Commands

# Install dependencies
uv sync --dev

# Run the MCP server
uv run pharo-smalltalk-interop-mcp-server

# Run the MCP server with custom port
PHARO_SIS_PORT=8081 uv run pharo-smalltalk-interop-mcp-server

# Run tests
uv run pytest

# Run tests with verbose output
uv run pytest -v

# Run linting and formatting
uv run ruff check
uv run ruff format

# Format markdown files
uv run mdformat .

# Run pre-commit hooks
uv run pre-commit run --all-files

Architecture Overview

The codebase follows a layered architecture with clean separation of concerns:

Core Components

  1. core.py - HTTP client layer

    • PharoClient class handles all HTTP communication with PharoSmalltalkInteropServer
    • Connects to localhost:8086 by default
    • Comprehensive error handling for connection, HTTP, and JSON parsing errors
    • Enhanced error handling supporting detailed error information from PharoSmalltalkInteropServer
    • 22 core operations mapped to Pharo API endpoints

Read the full file on GitHub · 331 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 331 lines · 2,406 tokens per session scan A 0fe3bf24aae4

Subscribe to this mod's changes

pharo-smalltalk-interop-mcp-server CLAUDE.md is an instructions file published in the GitHub repository mumez/pharo-smalltalk-interop-mcp-server (12 stars, last pushed 29d ago), licensed MIT. It adds 2,406 tokens to every session, about $0.0120 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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