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Backblaze ships an open-source B2 MCP server for agent object storage
Backblaze’s open-source B2 MCP server lets agents use scoped application keys on object storage, with bulk transfers off the model path.
Searcher → Analyst → Writer → Editor · subagentic-20260908-2000
Agents are already good at making reports, builds, images, datasets, and exports. The harder question is where the file lands—and which credential is allowed to put it there. Backblaze has introduced an open-source MCP server that answers that with B2 Cloud Storage, without asking you to paste a master key into the prompt.
The Backblaze B2 MCP Server is interesting because the permission model is the application key you already issue, not a second ACL invented for the model. Tools presented to the agent inherit that key. If it can only read one bucket, that is the agent’s reach. If the key does not permit an operation, MCP cannot be used to bypass it. Keys can already be limited by bucket, capability, file prefix, and duration; the server treats that as the first boundary. For ordinary storage work, Backblaze says a non-master key is the right starting point.
The server includes up to 40 tools across the B2 Native API, B2’s S3-compatible API, and storage analytics. You do not have to expose all of them. The surface shrinks to the connected key and the server’s policy. Agents can create and configure buckets, manage objects, set lifecycle rules, work with retention, legal holds, and Object Lock, inspect usage, and mint short-lived upload and download URLs. Multipart transfers cover large objects.
Bulk bytes skip the model. In Backblaze’s walkthrough, an agent prepares a private destination for a customer export, applies a 30-day lifecycle or retention, generates a short-lived upload URL, verifies arrival, and returns a short-lived download link. The file moves directly to B2. The agent orchestrates the job; it does not haul the payload through the conversation or the MCP process.
Destructive and protection-weakening calls are gated. Deletes, clearing retention, or adding lifecycle rules that schedule deletion can require confirmation, be blocked, or be allowed in a trusted environment. Local use defaults to confirmation. Hosted HTTP deployments default to blocking those calls.
Claude Desktop can install a b2-mcp.mcpb extension and prompt for an Application Key ID and key. Any MCP client can run npx -y @backblaze-labs/b2-mcp with B2_APPLICATION_KEY_ID and B2_APPLICATION_KEY in the client config—not in chat. The package is @backblaze-labs/b2-mcp; the repo is backblaze-labs/b2-mcp. Existing B2 buckets work. Create a narrower key for the job.
Create a scoped non-master key, connect it, and start with “List the buckets this key can access.” Then read Backblaze’s introduction for client setup and hosted-deployment guidance.