fastmcp-builder 0.3.0

Generate complete, runnable FastMCP 3.x MCP servers from plain-English descriptions

mcpforge

One sentence. One command. A complete MCP server, ready to run.

mcpforge generates production-ready FastMCP 3.x MCP servers from plain-English descriptions. You describe what you want; it produces tools, input validation, error handling, a pytest test suite, run configuration, and client setup docs — all wired together and ready to inspect, validate, and install.

Features

• Plain-English generation — describe your server in natural language; Claude writes the implementation
• Complete project scaffold — tools, Pydantic input models, error handling, pyproject.toml, and a pytest suite generated together
• FastMCP 3.x native — output uses modern FastMCP decorators and transport configuration, not raw MCP protocol boilerplate
• Validate before running — mcpforge validate runs syntax, security, lint, import, and pytest checks against generated servers
• Iterate safely — mcpforge update modifies an existing generated server and backs up changed files before writing
• Discover generated servers — mcpforge list finds mcpforge-generated projects in a workspace
• Inspect and diagnose — mcpforge inspect summarizes generated server shape, while mcpforge doctor checks local readiness
• Machine-readable output — status-like commands expose --json for agent workflows
• OpenAPI curation controls — include/exclude tags, operation allowlists, and operation limits keep generated integrations focused
• Scaffold without an LLM — mcpforge init creates a minimal FastMCP server skeleton for local iteration
• MCP server mode — mcpforge-server exposes generation, planning, validation, inspection, doctor, and discovery tools so AI assistants can build safely

Quick Start

Prerequisites

• Python 3.12+
• uv (recommended)
• Anthropic API key

Installation

uv tool install fastmcp-builder

The PyPI distribution is fastmcp-builder; the installed commands remain mcpforge and mcpforge-server.

Usage

# Generate a new MCP server
mcpforge generate "A todo list manager with create, read, update, and delete operations"

# Validate an existing generated server
mcpforge validate ./my-server

# Modify an existing generated server
mcpforge update ./my-server "Add a tool to export todos as CSV"

# Find generated servers in the current workspace
mcpforge list . --recursive

# Inspect a generated server without executing it
mcpforge inspect ./my-server

# Check local prerequisites and provider readiness
mcpforge doctor

Useful generation flags:

• --dry-run displays the structured plan without writing files.
• --no-execute writes files but skips import and test execution.
• --strict treats lint errors as hard validation failures.
• --from-openapi FILE generates from an OpenAPI 3.x spec.
• --openapi-include-tag TAG, --openapi-exclude-tag TAG, --openapi-operation ID, and --openapi-limit N curate OpenAPI conversion.
• --language python|typescript chooses the target server language.
• --provider anthropic|openai selects the generation provider. OpenAI is listed as planned and remains gated until deterministic structured-output smokes are implemented.

Useful status flags:

• mcpforge list --json
• mcpforge inspect PATH --json
• mcpforge validate PATH --json
• mcpforge doctor --json
• mcpforge version --json

Tech Stack

Layer	Technology
Language	Python 3.12+
Generation	Anthropic Claude via anthropic SDK
MCP framework	FastMCP 3.x
CLI	Click 8
Templates	Jinja2
Validation	Pydantic v2
Output	Rich

Architecture

The generate command sends the user's description to Claude with a structured prompt that includes FastMCP 3.x idioms and a tool-schema contract. Claude returns a JSON plan (tool names, signatures, and descriptions) that mcpforge validates against a Pydantic model before rendering through Jinja2 templates into a complete project directory. The generated project is then validated with syntax checks, security scanning, ruff linting, import checks, and pytest execution. The update command reads an existing generated server, asks Claude for a targeted modification, writes backups for changed files, and validates the result.

Current Status

As of May 10, 2026, main is prepared as 0.3.0 for the fastmcp-builder PyPI distribution. The v0.3 builder lane expands mcpforge from runnable-server generation into a production integration builder with inspection, doctor checks, richer generated scaffolds, OpenAPI curation, MCP server parity, provider abstraction, and live generated fixture examples for REST API, filesystem, database, and TypeScript profiles. See docs/CURRENT-STATE.md and docs/ROADMAP-v0.3.md.

License

MIT