Elasticsearch MCP: index_not_found_exception (the index name is wrong)

TL;DR: The cluster is fine; the index name is wrong. List the indices that actually exist and fix the name in your query. Typos and date-suffixed index patterns are the usual culprits.

{"error":{"root_cause":[{"type":"index_not_found_exception","reason":"no such index [logs-2026.10.02]"}]}}

Fix it

1. List the indices that exist. Use the MCP server's list-indices tool, or curl:

curl -u elastic:YOUR_PASSWORD "your-cluster/_cat/indices?v"

Expected: a table of index names. Compare against the name in your query.

1. Fix the name. Common mistakes:

• Date math: logs-2026.10.02 vs logs-2026-10-02 (dots vs dashes).
• Aliases vs concrete names: query the alias, not the backing index, or vice versa.
• Case: index names are lowercase by convention; uppercase fails.

1. If the index should exist but does not, create it or check you are pointed at the right cluster (dev vs prod URLs get mixed up).

Expected: the search returns hits instead of the exception.

When to use this

• Auth and connection work, but searches fail with index_not_found_exception.
• The index name contains a date or was typed by hand.

When NOT to use this

• The error is 401 or 403. That is auth, not the index name.
• All indices are missing. Then you are pointed at the wrong cluster.

Compatibility

• elastic/mcp-server-elasticsearch, any Elasticsearch client.
• Elasticsearch 7.x, 8.x.

Why it happens

Elasticsearch treats index names as exact identifiers with no fuzzy matching. MCP agents often construct index names from dates or guess them from context, and a single wrong character produces this error instead of results. It is the search equivalent of a typo in a table name.

Edge cases

• Wildcards (logs-*) avoid the exact-name problem but can hit too many indices. Prefer them for exploration, exact names for production queries.
• Data streams have a backing-index naming scheme. Query the data stream name, not the .ds- backing index.
• If the index was just created, allow a moment for cluster state to propagate, though this is rarely the issue.