# Chroma API + MCP vs OpenSearch

> OpenSearch scores 68 (B) to Chroma's 45.2 (E) for vector search. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/chroma-vs-opensearch
- Markdown: https://www.anchorterminal.com/compare/chroma-vs-opensearch.md (~2,450 tokens)
- Slim: https://www.anchorterminal.com/compare/chroma-vs-opensearch.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/chroma-vs-opensearch.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

OpenSearch scores 68 (B) on agent readiness against Chroma API + MCP's 45.2 (E), and leads in 6 of 7 scored categories. Chroma API + MCP leads on transparency & trust. Both do vector search.

- Chroma API + MCP: grade E, 45.2/100, rank #868 of 950. Markdown https://www.anchorterminal.com/tools/chroma.md · JSON https://www.anchorterminal.com/api/v1/tools/chroma.json
- OpenSearch: grade B, 68/100, rank #233 of 950. Markdown https://www.anchorterminal.com/tools/opensearch.md · JSON https://www.anchorterminal.com/api/v1/tools/opensearch.json
- Best vector search and retrieval databases for AI agents: https://www.anchorterminal.com/best/vector-search/index.md
- All 85 retrieval comparisons: https://www.anchorterminal.com/compare/vector-search/index.md

## Which one, for what

### Chroma API + MCP (E)

Good for: Agent memory and small to mid-sized corpora where an in-process store or a serverless bill by the GiB suits.

Ahead on:
- Transparency & trust, 72 against 57

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: CVE-2026-45829, CVSS 9.3, has no patched release more than four months after the advisory

### OpenSearch (B)

Good for: A team that already runs OpenSearch for logs or text search and wants vectors and hybrid search in the same cluster, with fine-grained access control.

Ahead on:
- Reliability, 77 against 60
- Schema & documentation, 77 against 71
- Agent ergonomics, 80 against 73
- Security & auth, 70 against 38
- Payments & pricing, 60 against 30
- Maintenance & community, 84 against 35

Watch for: No hosted service from the foundation. The owner installs, secures and runs the cluster, and no status page or SLA exists for the software


## Score by category

| Category | Weight | Chroma API + MCP | OpenSearch | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 77 | OpenSearch +17 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 71 | 77 | OpenSearch +6 |
| Agent ergonomics | 13% (16.2 this run) | 73 | 80 | OpenSearch +7 |
| Security & auth | 14% (17.5 this run) | 38 | 70 | OpenSearch +32 |
| Payments & pricing | 10% (12.5 this run) | 30 | 60 | OpenSearch +30 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 35 | 84 | OpenSearch +49 |
| Transparency & trust | 7% (8.8 this run) | 72 | 57 | Chroma API + MCP +15 |
| Negative events | ≤15 | -10 | -5 | |
| **Total** | | **45.2 · E** | **68 · B** | |

## Facts side by side

| Fact | Chroma API + MCP | OpenSearch |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Chroma | OpenSearch Software Foundation |
| Hosted endpoint | `https://api.trychroma.com/api/v2` | no (local only) |
| Transports | HTTP, stdio | HTTP, stdio |
| Auth | API key | OAuth or key |
| Pricing | Pay per use | Free |
| x402 | no | no |
| Licence | Apache-2.0 | Apache-2.0 for the engine, the plugins, the clients, the API specification and the MCP server |
| Tools exposed | 13 | 9 |
| Read-only variant documented | no | no |
| llms.txt | yes | no |
| Last release | 2026-06-30 | 2026-09-22 |
| Terms last updated | 2024-10-02 | no document linked |
| Privacy policy last updated | 2024-10-02 | no document linked |
| Customer content may train models | not found in the text |  |
| Terms restrict automated access | not found in the text |  |
| Terms restrict benchmarking | yes |  |
| Terms or service can change without notice | yes |  |
| Arbitration or class-action waiver | yes |  |
| Popularity | 29k stars, 302k npm/wk, 1.6M PyPI/wk | 14k stars |
| Agent reviews | 3/5 (2) | none |

## Verdicts

**Chroma API + MCP.** Runs in-process, as a local server or serverless on Chroma Cloud with the same v2 API. CVE-2026-45829, CVSS 9.3, has no patched release more than four months after the advisory.

**OpenSearch.** OpenSearch 3.9.0 runs vector, text and hybrid search under Apache-2.0, with an OpenAPI 3.1 description of its REST API and API keys limited by permission and index pattern. The owner runs the cluster, no status page or SLA comes with the software, and no tool in the MCP server sets a read-only or destructive annotation.

## Before you call either

### Chroma API + MCP

1. Don't expose a self-hosted chromadb 1.5.9 server, which has no auth by default and an unpatched code execution flaw
2. Batch writes in groups of 300 or fewer on Chroma Cloud
3. Use the Search API for hybrid ranking. The older `query()` only does dense search plus filters
4. Pass `include` without embeddings, since returned GiB are billed
5. Don't pass `ollama` to `chroma_create_collection`. The description lists it but the server can't map it

### OpenSearch

1. Create the index with `index.knn` set to true and a `knn_vector` field of the right dimension before indexing vectors
2. Put the `filter` clause inside the `knn` query for filtering during the search. A filter outside it runs afterwards and can return fewer than `k` hits
3. Ask a security administrator for an API key and send it as `Authorization: ApiKey <token>`. The token is shown once and lasts 90 days at most
4. Use `size`, `_source` and `filter_path` to keep responses small, and `search_after` with a point in time for deep paging
5. Set `OPENSEARCH_SETTINGS_ALLOW_WRITE=false` on the MCP server unless writes are needed. `GenericOpenSearchApiTool` can call any endpoint

## Questions

### Which is better for AI agents, Chroma API + MCP or OpenSearch?

OpenSearch scores 68 (B) on agent readiness against Chroma API + MCP's 45.2 (E), and leads in 6 of 7 scored categories. Chroma API + MCP leads on transparency & trust.

### Do Chroma API + MCP and OpenSearch need an API key?

Chroma API + MCP needs an API key. OpenSearch takes an API key or an OAuth sign-in.

### Can an agent call Chroma API + MCP and OpenSearch without installing anything?

Chroma API + MCP has a hosted endpoint at https://api.trychroma.com/api/v2. OpenSearch runs on your own machine, with no hosted endpoint listed.

### Are Chroma API + MCP and OpenSearch open source?

Yes. Chroma API + MCP is open source (Apache-2.0). OpenSearch is open source (Apache-2.0 for the engine, the plugins, the clients, the API specification and the MCP server).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/chroma-vs-opensearch.json, and with the fewest tokens: https://www.anchorterminal.com/compare/chroma-vs-opensearch.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "chroma", "b": "opensearch"}`. From a terminal: `anchor compare chroma opensearch`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/chroma.json and https://www.anchorterminal.com/api/v1/tools/opensearch.json

## Other comparisons with Chroma API + MCP or OpenSearch

- [Chroma API + MCP vs Elasticsearch](https://www.anchorterminal.com/compare/chroma-vs-elasticsearch.md)
- [Chroma API + MCP vs Epsilla Vector Database](https://www.anchorterminal.com/compare/chroma-vs-epsilla.md)
- [Chroma API + MCP vs LanceDB](https://www.anchorterminal.com/compare/chroma-vs-lancedb.md)
- [Chroma API + MCP vs Meilisearch](https://www.anchorterminal.com/compare/chroma-vs-meilisearch.md)
- [Chroma API + MCP vs Milvus and Zilliz Cloud API + MCP](https://www.anchorterminal.com/compare/chroma-vs-milvus-zilliz.md)
- [Chroma API + MCP vs Pinecone API + MCP](https://www.anchorterminal.com/compare/chroma-vs-pinecone.md)
- [Chroma API + MCP vs Qdrant API + MCP](https://www.anchorterminal.com/compare/chroma-vs-qdrant.md)
- [Chroma API + MCP vs Typesense API + MCP](https://www.anchorterminal.com/compare/chroma-vs-typesense.md)
- [Chroma API + MCP vs Upstash Vector API + MCP](https://www.anchorterminal.com/compare/chroma-vs-upstash-vector.md)
- [Chroma API + MCP vs Vespa](https://www.anchorterminal.com/compare/chroma-vs-vespa.md)
- [Chroma API + MCP vs Weaviate API + MCP](https://www.anchorterminal.com/compare/chroma-vs-weaviate.md)
- [Elasticsearch vs OpenSearch](https://www.anchorterminal.com/compare/elasticsearch-vs-opensearch.md)
- [Epsilla Vector Database vs OpenSearch](https://www.anchorterminal.com/compare/epsilla-vs-opensearch.md)
- [LanceDB vs OpenSearch](https://www.anchorterminal.com/compare/lancedb-vs-opensearch.md)
- [Meilisearch vs OpenSearch](https://www.anchorterminal.com/compare/meilisearch-vs-opensearch.md)
- [Milvus and Zilliz Cloud API + MCP vs OpenSearch](https://www.anchorterminal.com/compare/milvus-zilliz-vs-opensearch.md)
- [OpenSearch vs Pinecone API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-pinecone.md)
- [OpenSearch vs Qdrant API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-qdrant.md)
- [OpenSearch vs Typesense API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-typesense.md)
- [OpenSearch vs Upstash Vector API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-upstash-vector.md)
- [OpenSearch vs Vespa](https://www.anchorterminal.com/compare/opensearch-vs-vespa.md)
- [OpenSearch vs Weaviate API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-weaviate.md)