Weaviate MCP: vectorizer module not enabled (set ENABLE_MODULES)

TL;DR: Your Weaviate instance does not have the vectorizer module your collection needs. Enable it with ENABLE_MODULES at container startup (e.g. text2vec-openai), provide its API key, and recreate the collection.

vectorizer: module "text2vec-openai" not enabled

Fix it

1. Check which modules the instance runs:

curl https://your-cluster.weaviate.cloud/v1/meta | python3 -m json.tool

Look under modules.

2. For Docker, enable the module at startup:

docker run -d --name weaviate -p 8080:8080 -p 50051:50051 \
  -e ENABLE_MODULES=text2vec-openai \
  -e OPENAI_APIKEY [your value] \
  semitechnologies/weaviate:latest

3. Collections created before the module was enabled will not magically gain vectors. Recreate the collection (or re-import) after enabling.

4. Restart the MCP client.

   Expected: vector search works.

When to use this

• The error names a vectorizer module as not enabled or not found.
• Vector search fails on a fresh self-hosted instance while keyword search works.

When NOT to use this

• Weaviate Cloud. Modules there are managed; pick a supported vectorizer in the collection config instead.
• The error is about the API key for the vectorizer (invalid key). Enablement is fine; the key is wrong.

Compatibility

• weaviate/mcp-server-weaviate against self-hosted Weaviate.
• text2vec-openai, text2vec-cohere, text2vec-transformers modules.

Why it happens

Weaviate core does not vectorize text by itself; modules do. The Docker image enables only what ENABLE_MODULES lists, defaulting to none. Collections reference a vectorizer by name, and at query time Weaviate discovers the module is absent.

Edge cases

• text2vec-transformers runs a local model and needs significant RAM. Prefer an API-based vectorizer on small machines.
• Changing the vectorizer on an existing collection requires re-importing all objects. There is no in-place migration.
• Module names are versioned in newer Weaviate. Check the docs for the exact module name for your version.

Weaviate vectorizes text through modules (text2vec-openai, text2vec-cohere, text2vec-transformers) that must be enabled at instance startup via ENABLE_MODULES. A Weaviate instance started without the needed module rejects vectorizer-dependent operations. The weaviate-cloud secure coding rules show collections configured with vectorizer settings, and the standard fix for missing-vectorizer errors is enabling the module in the Docker environment or choosing a vectorizer the instance actually runs.