fieldflow

Overview

FieldFlow is a Python-based tool that transforms OpenAPI-described REST endpoints into selectively filtered tools. It dynamically generates Pydantic models and FastAPI routes that proxy requests to upstream APIs while returning only the fields specified by the caller. The project offers both HTTP server and MCP server modes, with the latter exposing OpenAPI tools through Model Context Protocol. It supports authentication schemes, nested field selection with JSONPath-like syntax, and includes CLI tools for reducing noisy JSON output.

Try asking AI

After installing, here are 5 things you can ask your AI assistant:

• get_user_info

  Fetch user information from JSONPlaceholder API with field selection

  Try:Get user 1's name and emailTry:Fetch user details for user_id 5 with only the name and email fields
• list_posts

  List posts for a user from JSONPlaceholder API with field selection

  Try:List posts for user 1 with just the title and idTry:Get all posts from user 2 showing only title and creation date
• pokemon_read

  Retrieve Pokemon information from PokeAPI with nested field selection

  Try:Get Pokemon 150's name, types, and attack statTry:Fetch Bulbasaur's data showing only name and type names
• ability_list

  List Pokemon abilities from PokeAPI with field selection

  Try:List the first 5 abilities with just their namesTry:Get abilities showing only result names
• ability_read

  Read a specific Pokemon ability by ID from PokeAPI

  Try:Get ability 65 with name and effect entriesTry:Fetch ability details showing only the ability name

Note: Tools are derived from OpenAPI specs and exposed through MCP server. Example tool calls shown in README demonstrate the field selection functionality.

Comparable tools

Installation

# Install with MCP support
pip install -e '.[mcp]'

# Run HTTP server
fieldflow serve-http

# Run MCP server (for Claude Desktop)
fieldflow-mcp

{
  "mcpServers": {
    "fieldflow": {
      "command": "python",
      "args": ["-m", "fieldflow_mcp.cli"]
    }
  }
}

FAQ

What authentication methods does FieldFlow support?

FieldFlow supports Bearer tokens (OAuth 2.0, JWT), API keys, Basic authentication, and automatic handling of OpenAPI-defined security schemes.

How does FieldFlow reduce response payload size?

FieldFlow accepts a 'fields' parameter in requests that allows selecting specific data fields. It uses JSONPath-like syntax to select nested fields and arrays, returning only the requested data.

On Hacker News

Recent discussion from the developer community.

• Show HN: Transform your REST API into optimized MCP server in one command line▲ 2
  Story by ggay · 2025-09-23

Compare fieldflow with