Checked other resources

• This is a bug, not a usage question.
• I added a clear and descriptive title that summarizes this issue.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
• This is not related to the langchain-community package.
• I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Package (Required)

• langchain
• langchain-openai
• langchain-anthropic
• langchain-classic
• langchain-core
• langchain-model-profiles
• langchain-tests
• langchain-text-splitters
• langchain-chroma
• langchain-deepseek
• langchain-exa
• langchain-fireworks
• langchain-groq
• langchain-huggingface
• langchain-mistralai
• langchain-nomic
• langchain-ollama
• langchain-openrouter
• langchain-perplexity
• langchain-qdrant
• langchain-xai
• Other / not sure / general

Related Issues / PRs

Reproduction Steps / Example Code (Python)

from langchain_mongodb.agent_toolkit import MongoDBDatabase, MongoDBDatabaseToolkit 
# Connection configuration 
MONGO_URI = "mongodb://<USERNAME>:<PASSWORD>@<PROJECT_ID>.us-central1.firestore.goog:443/?loadBalanced=true&tls=true&authMechanism=SCRAM-SHA-256&retryWrites=false" 
DB_NAME = "<DATABASE_NAME>" 
# Initialize MongoDB database 
db = MongoDBDatabase.from_connection_string( MONGO_URI, database=DB_NAME, ) 
# Initialize toolkit 
toolkit = MongoDBDatabaseToolkit( db=db, llm=llm, ) 
tools = toolkit.get_tools()

Error Message and Stack Trace (if applicable)

pymongo.errors.OperationFailure: authorizedCollections is not supported
full error: {
  'ok': 0.0,
  'errmsg': 'authorizedCollections is not supported',
  'code': 2,
  'codeName': 'InvalidArgument'
}

Description

Issue

MongoDB Toolkit fails when used with a Firestore MongoDB-compatible endpoint because the authorizedCollections option is not supported.

Description

When initializing MongoDBDatabase, LangChain internally executes a listCollections command via PyMongo. The MongoDB driver includes the option authorizedCollections=true.

Firestore's MongoDB-compatible endpoint rejects this option and returns the following error:

pymongo.errors.OperationFailure: authorizedCollections is not supported
full error: {
  'ok': 0.0,
  'errmsg': 'authorizedCollections is not supported',
  'code': 2,
  'codeName': 'InvalidArgument'
}

Because of this, MongoDBDatabase initialization fails and the MongoDB Toolkit cannot be used with the Firestore MongoDB-compatible endpoint.

Behavior Observed The MongoDB Toolkit works correctly when connecting to a standard MongoDB instance. When connecting to a Firestore MongoDB-compatible endpoint, initialization fails due to the unsupported authorizedCollections parameter.

What I Tested Tested in a local environment -> same error Deployed in Google Cloud Run -> same error

Since the error occurs in both environments, it appears to be related to compatibility with Firestore’s MongoDB-compatible layer rather than a networking issue.

Expected Behavior

One of the following would help:

• MongoDB Toolkit should gracefully handle MongoDB-compatible endpoints that do not support authorizedCollections, or
• Documentation should clarify that the MongoDB Toolkit only supports full MongoDB deployments.

Additional Context

Firestore provides a MongoDB-compatible API but does not implement the full MongoDB command set. I could not find documentation indicating whether LangChain MongoDB Toolkit supports this compatibility layer.

Environment

• LangChain version: 1.2.15
• langchain-mongodb version: 0.11.0
• PyMongo version: 4.16.0
• Python version: 3.13

Deployment:

Local machine Google Cloud Run

Database: Firestore MongoDB-compatible endpoint

System Info

System Information

OS: Linux OS Version: #106~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Mar 6 08:44:59 UTC Python Version: 3.10.12 (main, Mar 3 2026, 11:56:32) [GCC 11.4.0]