How to Integrate Fastio API with LangChain Tools

LangChain agents need file storage that lasts longer than short-term memory. Fastio gives API-first workspaces. Built-in features include RAG, versioning, and ownership transfers to people. Agents set up project folders, search docs by meaning, and send branded shares.

Other storage means you handle indexing or vector DBs. Turn on intelligence mode in Fastio, and it indexes files on its own. Agents get multiple free storage plus multiple monthly credits. No credit card needed.

Developers find this easier when building tools for production.

Helpful references: Fastio Workspaces, Fastio Collaboration, and Fastio AI.

Sign up for a Fastio agent account at fast.io (no credit card needed). Create an API key in Settings > API Keys.

Install dependencies:

pip install langchain langchain-community requests python-dotenv

Set your API key:

FASTIO_API_KEY=your_key_here
FASTIO_BASE_URL=https://api.fast.io/current

Base URL for API calls is https://api.fast.io/current/.

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Extend LangChain's BaseTool for Fastio operations. Start with listing workspace files.

from langchain.tools import BaseTool
from typing import Optional
import requests
import os
from dotenv import load_dotenv

load_dotenv()

class FastIOLister(BaseTool):
    name = "fastio_list_workspace_files"
    description = "List files in a Fastio workspace. Useful for finding documents to analyze."

def _run(self, workspace_id: str) -> str:
        headers = {"Authorization": f"Bearer {os.getenv('FASTIO_API_KEY')}"}
        url = f"{os.getenv('FASTIO_BASE_URL')}/workspace/{workspace_id}/storage/root/"
        resp = requests.get(url, headers=headers)
        resp.raise_for_status()
        data = resp.json()
        files = [node['name'] for node in data['response'] if node['type'] == 'file']
        return f"Files: {', '.join(files[:10])}"  # First 10

Authenticate with POST /current/user/auth/ using Basic Auth first to get JWT, but API keys work directly as Bearer.

Next, define a FastIOReader tool.

class FastIOReader(BaseTool):
    name = "fastio_read_file"
    description = "Read content from a file in Fastio workspace. Input workspace_id and node_id."

def _run(self, workspace_id: str, node_id: str) -> str:
        headers = {"Authorization": f"Bearer {os.getenv('FASTIO_API_KEY')}"}
        url = f"{os.getenv('FASTIO_BASE_URL')}/workspace/{workspace_id}/storage/{node_id}/content/"
        resp = requests.get(url, headers=headers)
        resp.raise_for_status()
        return resp.text[:5000]  # Truncate for context

Use storage/{node_id}/content/ for text files, /preview/ for rendered.

Combine tools in an agent.

from langchain_openai import ChatOpenAI
from langchain.agents import create_tool_calling_agent, AgentExecutor
from langchain_core.prompts import ChatPromptTemplate

llm = ChatOpenAI(model="gpt-4o")
tools = [FastIOLister(), FastIOReader()]
prompt = ChatPromptTemplate.from_messages([("system", "You manage files in Fastio."), ("human", "{input}"), ("placeholder", "{agent_scratchpad}")])
agent = create_tool_calling_agent(llm, tools, prompt)
agent_executor = AgentExecutor(agent=agent, tools=tools)
result = agent_executor.invoke({"input": "List files in workspace multiple and read the first report."})

Agents now handle file ops natively.

Enable intelligence on workspace via PATCH /current/workspace/{id}/ with intelligence: true. Files auto-index for semantic search.

Use AI chat endpoint POST /current/workspace/{id}/ai/chat/ for RAG queries. Create custom tool:

class FastIORAG(BaseTool):
    ### Implementation for POST /ai/chat/ with folders_scope
    pass

Get context from multiple files right away. Search across docs with citations.

• 401 Unauthorized: Check API key permissions.
• multiple Too Large: Chunk uploads for >multiple files via /upload/.
• No RAG results: Verify ai_state: ready on files.
• Rate limits: Headers show remaining calls.