Redis MCP: NOAUTH Authentication required (set REDIS_PWD)

TL;DR: NOAUTH means the Redis MCP server connected without a password to a Redis that requires one. Set REDIS_PWD in the server's environment (and REDIS_USERNAME if you use ACL users) and restart. Every command will start working.

NOAUTH Authentication required.

Fix it

1. Confirm the Redis side requires auth. If you run it, check for --requirepass or requirepass in the config. If it is managed (Upstash, Redis Cloud), it always requires auth.
2. Set the credentials in the MCP server's environment. In your client config env block, or wherever you launch the server:

REDIS_HOST=your-redis-host
REDIS_PORT=6379
REDIS_USERNAME=default
REDIS_PWD=your-redis-password

Command-line args take precedence over env vars if your setup passes --url explicitly. Make sure the password is in the URL then: redis://:password@host:6379/0.

3. Restart the MCP server (restart the client for stdio servers).

   Expected: tools execute and return data. PING returns PONG.

When to use this

• Every Redis tool call fails with NOAUTH Authentication required.
• redis-cli -a [password] ping works, proving the server and password are fine.

When NOT to use this

• The error is WRONGPASS. A password is being sent, it is just wrong. Fix the value, not the presence.
• The error is a connection timeout or refused. The server is not reachable at all.

Compatibility

• redis/mcp-redis (env-var and --url configuration).
• Redis 6+ with ACLs, Redis 7, Upstash, Redis Cloud, self-hosted with requirepass.

Why it happens

The Redis MCP server defaults to no password (REDIS_PWD empty). That matches a default local Redis, but any production or managed Redis requires auth. The server does not prompt or fail at startup; it connects and then every command gets NOAUTH, which looks like the server is broken when it is just unauthenticated.

Edge cases

• With ACLs, an empty username sends a one-arg AUTH that fails differently. Set REDIS_USERNAME=default explicitly when using the default user with a password.
• Special characters in the password inside a --url must be percent-encoded.
• Docker setups: the env var must be passed into the container (-e REDIS_PWD=...), not just set on the host.

The redis/mcp-redis server reads connection settings from environment variables including REDISHOST, REDISPORT, REDISUSERNAME and REDISPWD, documented in the project's configuration guides (zskbot/catalog image/redis-mcp/guides.md, upstream https://github.com/redis/mcp-redis). When the Redis server runs with --requirepass and the MCP server has no password configured, every command fails with NOAUTH Authentication required. The same failure is documented in deployment guides: REDIS_URL had no credentials while the server runs with --requirepass, so clients failed with NOAUTH.