How to Connect ChatGPT to Reddit (Custom GPT Actions + Function Calling)

Connect ChatGPT to Reddit two ways: import a Reddit API's OpenAPI spec as a Custom GPT Action (no code), or wire the same API in as a tool with OpenAI function calling (your own app). ChatGPT has no Reddit search built in by default — the same gap Claude has (see why Claude Code can't search Reddit for why) — so one of these two setups is required either way.

How do I add Reddit to a Custom GPT?

In the GPT builder, open Configure → Actions → Create new action, then Import from URL and paste:

https://api.threadsnoop.com/openapi.json

Set Authentication to API Key, auth type Custom, header name x-api-key, and paste your key. Save, and every endpoint — search_posts, search_comments, get_comment_tree, and the rest — is now something your GPT can call. Ask it “find posts in r/freelance from this week about invoicing clients” and it plans the call, hits the API, and reads the results back to you.

How do I use Reddit with OpenAI function calling?

Building your own app instead of a Custom GPT, the same API works as a tool definition against OpenAI's function calling:

import json, requests
from openai import OpenAI

client = OpenAI(api_key="YOUR_OPENAI_KEY")
tools = [{
    "type": "function",
    "function": {
        "name": "search_reddit_posts",
        "description": "Search Reddit posts via the ThreadSnoop API",
        "parameters": {
            "type": "object",
            "properties": {
                "subreddit": {"type": "string"},
                "q": {"type": "string", "description": "exact-phrase filter"},
            },
            "required": ["subreddit"],
        },
    },
}]

response = client.chat.completions.create(
    model="gpt-4o",  # any tool-calling-capable model works
    messages=[{"role": "user", "content": "Find recent r/smallbusiness posts about invoicing"}],
    tools=tools,
)

call = response.choices[0].message.tool_calls[0]
args = json.loads(call.function.arguments)
posts = requests.get(
    "https://api.threadsnoop.com/v1/posts",
    headers={"x-api-key": "YOUR_THREADSNOOP_KEY"},
    params=args,
).json()

Same read-only rule as everywhere else: this fetches Reddit, it doesn't post to it. (Wiring a fuller agent loop, with pagination: using AI agents to search Reddit — Claude's MCP version: giving Claude access to Reddit — and the same OpenAPI spec used directly from a shell, no MCP or Actions config at all: giving Claude Code access via an OpenAPI spec.)

Frequently asked questions