Backblaze B2 MCP Server

A Model Context Protocol server for Backblaze B2 Cloud Storage. It lets any MCP-compatible AI client (Claude, and others) operate B2 through a focused, safe set of tools, currently incubating in Backblaze-Labs.

This is the official Backblaze B2 MCP server — backblaze-labs/b2-mcp, published as @backblaze-labs/b2-mcp on npm and listed in the Official MCP Registry as io.github.backblaze-labs/b2-mcp. Community forks and third-party wrappers are not maintained by Backblaze.

40 tools, assigned by backing category:

• Native B2 SDK (@backblaze-labs/b2-sdk) (17) — B2 control-plane operations the S3 API has no equivalent for: buckets, application keys, Object Lock, event notifications, and Partner/Groups operations.
• AWS S3 SDK (@aws-sdk/client-s3) (19) — the S3-compatible data plane: object upload/download/copy/list/delete, multipart, bucket reachability, lifecycle, and presigned URL paths.
• Neither SDK (custom MCP code) (4) — repository-owned analytics over B2 reports and bounded live listings: storage growth, egress leaders, largest files, and abandoned uploads.

Destructive actions are gated, durable B2 secrets stay out of the model's context in the default/file/off modes, and registration is capability-aware so a key only ever sees tools it can use. The server also exposes read-only MCP resources: b2://server-config (non-secret, registered even during credential-less discovery), plus capability-gated b2://capabilities and b2://bucket/{bucketName}.

Contents

• Quick start
• B2 Skills pack
• Configuration
• Tools
• Package API Surface
• CLI Reference
• Resources
• Security & self-hosting
• Privacy
• Development
• Documentation

Quick start

Prerequisites: A supported Node.js runtime and a Backblaze B2 application key. A non-master key is all you need. The package engine range is ^22.22.2 || ^24 || ^26; CI runs on Node.js 22.23.1, 24, and 26. One non-master application key covers normal storage work (B2 native, S3, and key management); the Partner/Groups tools additionally need B2_MASTER_KEY_ID / B2_MASTER_KEY.

Option A — npx (Claude Desktop config)

Edit claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/, Windows: %APPDATA%\Claude\, Linux: ~/.config/Claude/) and add:

{
  "mcpServers": {
    "backblaze-b2": {
      "command": "npx",
      "args": ["-y", "@backblaze-labs/b2-mcp"],
      "env": {
        "B2_APPLICATION_KEY_ID": "your-application-key-id",
        "B2_APPLICATION_KEY": "your-application-key-secret"
      }
    }
  }
}

Restart Claude Desktop and the B2 tools appear. If you need an explicit fallback region before authorization, add B2_REGION to the same env block (S3/report tools otherwise derive their region from the authorized B2 account response):

{
  "B2_APPLICATION_KEY_ID": "your-application-key-id",
  "B2_APPLICATION_KEY": "your-application-key-secret",
  "B2_REGION": "us-east-005"
}

The canonical package name is @backblaze-labs/b2-mcp and the canonical binary is b2-mcp (b2-mcp-server is a transition alias); npx -y @backblaze-labs/b2-mcp runs it directly. See Configuration for the full variable list, and docs/product-specs/clients.md for a source-checkout setup and copy-paste configs for Cursor, VS Code, Cline, Windsurf, Zed, Continue, Goose, Claude.ai, and hosted (Streamable HTTP).

Option B — Claude Desktop extension (MCPB)

Available once a release publishes the b2-mcp.mcpb asset (0.2.1 onward); earlier releases carry no bundle, so use Option A until the asset appears on the releases page.

Prefer no JSON editing? Download b2-mcp.mcpb from the latest release, then in Claude Desktop open Settings → Extensions → Advanced settings → Extension Developer → Install Extension… and select the downloaded file. Claude Desktop prompts for your Application Key ID and Application Key (Region and Master keys optional) — no config file to hand-edit. The bundle launches a version-pinned npx -y @backblaze-labs/b2-mcp@<version> (npm resolves the server on first run) so it always runs the exact published version. A one-click Claude Connectors Directory listing is in progress.

Then just ask:

"List the buckets this key can access." · "Upload ./data.csv to reports/may-2026.csv." · "Give me a 1-hour download link for backups/latest.tar.gz." · "List files under logs/2026/."

Why your client may show fewer than 40 tools: registration is capability-aware. With a non-master key and no master key configured, the three Partner/Groups tools that require a master key are not surfaced, so tools/list reports 37; add B2_MASTER_KEY_ID / B2_MASTER_KEY on a Partner-entitled account for the full 40. A read-only key trims the surface further. Credential-free scanners see the full advertised surface, but every tools/call returns missing_credentials until valid B2 credentials are supplied.

Docker

The published image defaults to the HTTP transport and reads configuration only from environment variables (no mutable latest tag — pin the release version):

B2_MCP_VERSION=VERSION # replace with the release version you want
B2_MCP_IMAGE="ghcr.io/backblaze-labs/b2-mcp:${B2_MCP_VERSION}"
docker run --rm --name b2-mcp \
  --stop-timeout 20 \
  -p 127.0.0.1:3000:3000 \
  -e B2_HTTP_CREDENTIAL_MODE=server \
  -e B2_APPLICATION_KEY_ID=your-application-key-id \
  -e B2_APPLICATION_KEY=your-application-key-secret \
  -e B2_ALLOWED_HOSTS=localhost,127.0.0.1 \
  -e B2_DESTRUCTIVE_POLICY=block \
  -e B2_REGISTER_ALL_TOOLS=false \
  -e B2_SECRET_SINK=off \
  -e B2_ALLOW_INLINE_SECRETS=false \
  -e B2_ALLOW_LOCAL_FILES=false \
  "$B2_MCP_IMAGE"

For stdio clients inside a container, pass the transport explicitly and keep stdin open:

B2_MCP_VERSION=VERSION # replace with the release version you want
B2_MCP_IMAGE="ghcr.io/backblaze-labs/b2-mcp:${B2_MCP_VERSION}"
docker run --rm -i \
  --no-healthcheck \
  -e B2_APPLICATION_KEY_ID=your-application-key-id \
  -e B2_APPLICATION_KEY=your-application-key-secret \
  "$B2_MCP_IMAGE" stdio

Deploying to hosted HTTP? See the deployment matrix and provider guides (Docker, Vercel, Cloudflare, AWS, GCP, Azure, Render, Railway, Fly.io) linked from Security & self-hosting, and docs/references/deployment/docker.md for hardened HTTP examples.

B2 Skills pack