Chroma MCP: Collection does not exist (verify the collection name)

TL;DR: ChromaDB is up; the collection name is wrong. List the collections that exist, fix the name, retry.

Collection [my_docs] does not exist

Fix it

1. List the collections. Use the MCP server's list-collections tool, or:

curl http://YOUR_CHROMA_HOST:8000/api/v2/collections

Expected: JSON with the real collection names.

2. Fix the name in your tool call. Common mistakes: pluralization, dashes vs underscores, case.

3. If the collection should exist but does not, create it first with the create-collection tool, or check you are pointed at the right ChromaDB (dev vs prod data dirs get mixed up).

   Expected: queries run against the collection.

When to use this

• ChromaDB connects fine, but a specific collection is reported missing.
• The name was typed by hand or generated by the agent.

When NOT to use this

• Connection refused. ChromaDB is down.
• No collections exist at all. Create one first.

Compatibility

• chroma-mcp, rkilchmn/chroma-mcp-server.
• ChromaDB local and server modes.

Why it happens

Collection names are exact strings with no fuzzy matching. In persistent mode, each data directory is its own universe of collections, so pointing at a fresh or different directory looks exactly like a missing collection.

Edge cases

• Persistent mode: the data directory determines which collections exist. A new --path means zero collections.
• Collection names cannot be renamed. Create the correctly named one and migrate data.
• Some servers auto-create configured collections at startup. If yours does not, create them explicitly.

The chroma-mcp-server troubleshooting section (rkilchmn/chroma-mcp-server) lists Collection not found as a common issue with the fix: verify collection names are correct. ChromaDB collection names are exact, and MCP agents often guess or miscapitalize them. Source: https://github.com/rkilchmn/chroma-mcp-server