Prompt flow after the Bing Search API

The url field of BingConnection

Prompt flow declares the connection in promptflow/connections/__init__.py:

@dataclass
class BingConnection:
    api_key: Secret
    url: str = "https://api.bing.microsoft.com/v7.0/search"

Prompt flow ships no Bing tool of its own: the call is in a Python tool you wrote, which takes the connection as an input. We ran a tool of this shape. It reads connection.url, so it needs no change:

import requests
from promptflow.core import tool
from promptflow.connections import BingConnection


@tool
def bing_search(connection: BingConnection, question: str) -> list:
    reply = requests.get(
        connection.url,
        headers={"Ocp-Apim-Subscription-Key": connection.api_key},
        params={"q": question, "count": 10},
        timeout=60,
    )
    reply.raise_for_status()
    return reply.json()["webPages"]["value"]

Change the connection, in the connections file your run reads (the dev-connections.json form in Prompt flow's repository):

"bing_connection": {
  "type": "BingConnection",
  "module": "promptflow.connections",
  "value": {
    "api_key": "<your SpecStream key>",
    "url": "https://api.specstream.ai/v7.0/search"
  }
}

On Nov 12, 2026 we ran this flow with promptflow-core 1.18.5. The node finished with status Completed and returned the pages of webPages.value, each with its name, url and snippet.

A custom connection, the way the pf CLI stores it

The local pf connection store holds connection types such as custom, and a Microsoft answer on Q&A recommends a custom connection for a Bing key. Put the address in configs and the key in secrets:

$schema: https://azuremlschemas.azureedge.net/promptflow/latest/CustomConnection.schema.json
name: bing_search
type: custom
configs:
  url: "https://api.specstream.ai/v7.0/search"
secrets:
  api_key: "<your SpecStream key>"

pf connection create -f bing_search.yaml --set secrets.api_key=$SPECSTREAM_API_KEY

A tool that takes a CustomConnection reads connection.configs["url"] and connection.secrets["api_key"] and sends the same GET. We ran that tool too on Nov 12, 2026, with status Completed.

The same request and the same JSON

SpecStream answers GET /v7.0/search with q, count and offset in Bing's shape, with the key in Ocp-Apim-Subscription-Key. Every parameter and field of the route is in the Bing Web Search v7 guide, and what Microsoft ended, and when, is on the Bing Search API retirement page.

$1 per 1,000 searches, with no daily limit

A search of up to 10 results costs $0.001. There is no monthly plan and no daily limit. Credit you buy never expires, and a new account starts with $10 of credit, which covers 10,000 searches. A busy call gets a 429 with Retry-After and charges nothing.

The most accurate web search API, in about one second

On SimpleQA Verified the SpecStream Search API scores 97.9 F-score on all 1,000 official questions, 978 of them correct. On WideSearch it scores 64.0 item F1 and 43.4 row F1 on all 200 official tasks. Every score and its method is on the benchmarks page.

Every Bing call runs the fast search. Measured on production on November 9, 2026, its median was 0.82 s at 1 search a second and 1.07 s at 20 a second, and it answered 718 of 720.

The same key after Prompt flow retires

Microsoft retires Prompt flow in Microsoft Foundry and Azure Machine Learning on April 20, 2027 and asks you to move to Microsoft Agent Framework. Your search tool is a plain HTTP call, so it moves with you: the same address and the same key work from any Python code, as the Bing Search API in Python page shows.

Grounding with Bing Search

Microsoft's named replacement for the Bing Search APIs, at $14 per 1,000 transactions, inside Azure AI Agents. It returns an answer with citations, and developers get no access to the raw results, so a Prompt flow tool has no webPages.value to read. SpecStream returns Bing's webPages.value[] at $1 per 1,000.

Prompt flow's Serp API tool

The built-in tool wraps SerpApi's Google and Bing results. SerpApi sells plans from $25 a month for 1,000 searches, and the tool returns SerpApi's JSON, so a flow written for Bing's fields needs new parsing. SpecStream keeps your Bing tool and its fields, at $1 per 1,000 with no plan.

Google Custom Search JSON API

$5 per 1,000 queries after 100 free a day, up to 10,000 a day, for existing customers only: Google closed it to new customers and ends it on January 1, 2027. It answers a different request with a different reply. SpecStream keeps your Bing call and costs $1 per 1,000, with no daily limit.