Meilisearch vs OpenSearch

Meilisearch

Keyword, vector and hybrid search share one request, behind keys scoped by action and index and a published OpenAPI 3.1 file with 143 operations. The built-in MCP server is experimental and read-only, and Cloud access starts with a browser sign-up and a 14-day trial.

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.

Meilisearch

1. Create a key with only search, documents.get and indexes.get on the indexes needed. The default search key fails listIndexes and describeIndex over MCP
2. Enable the mcpRoute experimental feature first. Until then /mcp answers feature_not_enabled
3. For hybrid search send hybrid with an embedder name configured in the index settings and a semanticRatio from 0 to 1
4. Writes return a taskUid and run asynchronously. Poll the task before searching for the new documents
5. On 503 too_many_search_requests, wait for the Retry-After header (10 seconds) before retrying

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