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.

```text
vectorizer: module "text2vec-openai" not enabled
```

## Fix it

1. Check which modules the instance runs:

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

   Look under `modules`.

2. For Docker, enable the module at startup:

```bash
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.