Backblaze B2 MCP Server

Read from the package source without running it. The installed server may list more.

• b2_authorize_account

  Authorize with B2 and return account info including accountId, apiUrl, and downloadUrl. The server handles authorization automatically, but this tool is useful for verifying credentials and retrieving account details.

• b2_create_bucketwrite action

  Create a persistent B2 bucket with optional metadata, CORS, lifecycle, default encryption, and Object Lock enablement. Use for initial provisioning with a key that has writeBuckets; use b2_update_bucket for later settings changes and s3_head_bucket to check S3 reachability. Bucket names are globally unique, case-insensitive, 6-63 characters, letters/digits/hyphens/periods, and cannot start with 'b

• b2_create_group_memberwrite action

  Create a Backblaze account for a new Partner group member. In file sink mode, the one-time application key secret is written to the configured out-of-band secret sink and the MCP response contains only redacted metadata plus a secretSink pointer. In inline mode, the secret is returned with an explicit warning.

• b2_create_keywrite action

  Create a B2 application key and route its one-time secret through the configured secret sink. Use for least-privilege scoped credentials; use b2_list_keys to inspect existing keys and b2_delete_key to revoke retired keys. Requires writeKeys, idempotencyKey, and destructive confirmation by policy. File sink mode returns redacted metadata plus a secretSink pointer; inline mode returns the secret onl

• b2_delete_bucketwrite action

  Delete a B2 bucket. The bucket must be empty — all files and file versions must be deleted first.

• b2_delete_keywrite action

  Permanently delete a B2 application key. Use b2_list_keys first to verify applicationKeyId, keyName, capabilities, and dependent systems; use b2_create_key before deletion when rotating credentials. Requires deleteKeys and destructive confirmation by policy. The key secret cannot be recovered, and anything still using the deleted key loses access immediately.

• b2_eject_group_member

  Eject a member from a Group. The account is NOT deleted — just removed (the member resets their password on next login). Optionally change their email on eject. Cannot be re-added via API (only the Group Management page).

• b2_get_bucket_notification_rules

  Read the B2 event-notification webhook rules for a bucket. Use before b2_set_bucket_notification_rules to diff or preserve existing rules, because set replaces the complete rule set. Requires readBucketNotifications or writeBucketNotifications, has no side effects, and redacts webhook URL host/path/query, HMAC secrets, and custom-header values in the MCP response.

• b2_list_buckets

  List B2 buckets for the authorized account. Optionally filter by bucket ID, name, or type. When the key is bucket-scoped and no bucketId/bucketName filter is supplied, requests are automatically narrowed to the authorized bucket IDs. Returns bucket ID, name, type, CORS rules, and lifecycle rules for each bucket. Capped to `limit` buckets (default 100, max 1000) to keep the response small for accou

• b2_list_group_members

  List active (ACCEPTED) Group members for a specific Group. Returns up to 1,000 members per call; use nextEmail for pagination. Includes B2 storage stats per member.

• b2_list_groups

  List active Groups administered by a Group admin account. Returns up to 100 groups per call; use nextGroupId for pagination. Requires the account to be authorized for the Partner API.

• b2_list_keys

  List the application keys associated with the B2 account. Does not return the actual key secrets — only key IDs, names, capabilities, and restrictions.

• b2_list_largest_files

  List a bucket's largest objects by size via a live listing. For 'largest files', 'what's taking up space in <bucket>'. Give the bucket by name or bucketId; optional path prefix. Sorting by size requires a full listing, so on very large buckets the scan is bounded by max_scan and a time budget — it then returns the largest among the objects scanned with truncated=true; pass a prefix to focus on a s

• b2_rank_egress_leaders

  Rank top egress (downloaded bytes) by account or bucket over a period — default month-to-date. For 'who's downloading the most', 'where is egress concentrated'. Returns leaders with each one's share of total egress, from the daily usage reports. Scope follows the caller's key. Needs Usage Reports enabled.

• b2_report_usage_growth

  Rank accounts by how much STORED data grew or shrank between two points in time, from the daily B2 usage reports (uses stored_gb, the end-of-day snapshot). For 'which customers grew the most/least', 'who's moving data off'. Compares the latest snapshot against one month/quarter/year earlier and fetches only those two days, so it stays fast even on large report buckets. Returns the two dates compar

• b2_reserve_trial_create_accountwrite action
• b2_set_bucket_notification_rules

  Replace the complete B2 event-notification webhook rule set for a bucket. Use b2_get_bucket_notification_rules first and submit the full desired rule set; this is not a patch or append API. Requires writeBucketNotifications and destructive confirmation by policy. Each webhook URL must be a public HTTPS endpoint, and echoed URL details, HMAC secrets, and custom-header values are redacted from the r

• b2_unfinished_uploads

  Find abandoned multipart uploads that silently consume storage in a bucket. For 'bucket bloat', 'stuck/incomplete uploads', 'wasted storage'. Returns count, oldest upload age, and wasted bytes. Give the bucket by name or bucketId. Live listing, bounded by max_uploads and an internal time budget — on a very bloated bucket it returns a truncated result (and wasted_gb may be a lower bound) and recomm

• b2_update_bucketwrite action

  Update persistent settings on an existing B2 bucket: visibility, metadata, CORS, lifecycle, default encryption, replication, Object Lock, and default retention. Requires the writeBuckets capability. Use b2_list_buckets first to inspect the current bucketId/revision and use ifRevisionIs for safer retries; use s3_put_bucket_lifecycle only when you specifically need the S3 lifecycle API shape. Gated

• b2_update_file_legal_holdwrite action

  Set or clear a legal hold on a specific file version in B2. When a legal hold is active, the file cannot be deleted regardless of retention settings. Requires the writeFileLegalHolds capability on the application key.

• b2_update_file_retentionwrite action

  Set or modify the retention policy on a specific file version in B2. Supports governance and compliance retention modes. In compliance mode, the retain-until date can only be extended. Requires the writeFileRetentions capability.

• s3_abort_multipart_uploadwrite action

  Abort an in-progress S3-compatible multipart upload and release all associated storage.

• s3_complete_multipart_uploadwrite action

  Finalize an S3-compatible multipart upload in B2 by assembling uploaded parts. Use only after s3_create_multipart_upload and s3_get_presigned_upload_part_url (or s3_upload_part_copy) have produced every required part; use s3_list_parts to verify uploaded parts before retrying. Requires writeFiles. Completion is idempotent only when B2 already committed the exact same part list; if the response is

• s3_copy_object

  Copy an object within B2 or between B2 buckets via B2's S3-compatible CopyObject API. The acl input is retained as a no-op S3 compatibility hint; B2 access follows the destination bucket policy.

• s3_create_multipart_uploadwrite action
• s3_delete_objectwrite action

  Delete one B2 object through the S3-compatible API. Use s3_list_object_versions first when you need to target a specific version or delete marker; use s3_delete_objects for batches up to 1000. Requires deleteFiles and destructive confirmation by policy; targeting a specific versionId additionally requires readFiles, because native B2 version binding is verified first. Omitting versionId applies no

• s3_delete_objectswrite action

  Delete multiple objects from a B2 bucket with bounded SDK concurrency (up to 1000 objects).

• s3_get_bucket_location

  Get the region (location constraint) of a B2 bucket via the S3-compatible API. No native b2_* equivalent — used to verify region/endpoint pairing.

• s3_get_object

  Read a SMALL object inline (≤1 MiB, returned base64) — for manifests, sidecars, and configs the agent must inspect — or stream any size to a local path with saveToPath. saveToPath writes the fetched bytes to the local filesystem (creating parent directories), removes the partial file if the stream fails (cleanup of its own output only), and performs no mutation of B2 or any remote data. For real o

• s3_get_presigned_upload_part_urlwrite action

  Generate short-lived presigned PUT URL bearer capabilities for parts of an S3-compatible multipart upload, so the client/worker uploads each part DIRECTLY to B2. Prefer this over s3_get_presigned_url for multipart uploads; use s3_get_presigned_url for single-object PUT/GET transfers. The response includes expiresIn/expiresAt; treat each URL as sensitive until it expires. Flow: s3_create_multipart_

• s3_get_presigned_url
• s3_head_bucket

  Check whether a B2 bucket exists and is reachable on the S3-compatible endpoint with the current credentials. Use this to validate S3-surface reachability (the native b2_list_buckets confirms existence but not S3 reachability).

• s3_head_object

  Get metadata for a B2 object without downloading it. Returns content type, size, last modified, ETag, and custom metadata.

• s3_list_multipart_uploads

  List in-progress S3-compatible multipart uploads for a B2 bucket. Use to resume or audit unfinished uploads before s3_get_presigned_upload_part_url, s3_complete_multipart_upload, or s3_abort_multipart_upload; use b2_unfinished_uploads when you need storage-cost analysis across bounded listings. Requires listFiles. Results are paginated with maxUploads (default 100, range 1-1000) and key/upload mar

• s3_list_object_versions

  List object versions and delete markers in a B2 bucket using the S3-compatible API. Use before version-targeted s3_get_object, s3_head_object, s3_copy_object, or s3_delete_object calls; use s3_list_objects_v2 when current live objects are enough. Requires listFiles. Results are paginated with maxKeys (default 1000, max 1000) and paired key/version markers.

• s3_list_objects_v2

  List objects in a B2 bucket via the S3-compatible ListObjectsV2 API. Supports prefix filtering, delimiter-based folder listings, and pagination.

• s3_list_parts

  List the parts that have been uploaded for an in-progress S3-compatible multipart upload.

• s3_put_bucket_lifecyclewrite action

  Set S3 lifecycle rules on a B2 bucket; pass rules: [] to clear the S3 lifecycle configuration. Supports AbortIncompleteMultipartUpload, Expiration, and NoncurrentVersionExpiration. B2 does not support Transition/storage-class rules.

• s3_put_objectwrite action

  Upload a SMALL object inline (≤1 MiB) to a B2 bucket — for manifests, sidecars, and tiny configs. Provide base64-encoded content or a local file path. For real object data, generate a PutObject URL with s3_get_presigned_url and upload directly to B2 (bytes never pass through the server), or use the multipart tools for large objects.

• s3_upload_part_copywrite action

• Code scan113 source files scanned25/25
• –Live reliabilityno gateway calls yet and no remote to proben/a
• –Tool poisoningtools not inspected (local package is not executed); not countedn/a
• Auth qualitystatic API keys via environment variables6/15
• Maintenancelast push 6 days ago15/15
• Maintainer identityregistry namespace matches repository owner7/10

Backblaze B2 MCP Server: common questions

Is Backblaze B2 MCP Server safe?

Mostly: it is graded B (82/100). Read the Backblaze B2 MCP Server safety report

How do I install Backblaze B2 MCP Server?

It runs on your machine. Copy the Claude Code, Claude Desktop or Cursor config from the install section.

Does Backblaze B2 MCP Server need an API key?

Yes. The registry entry asks for B2_APPLICATION_KEY_ID, B2_APPLICATION_KEY, B2_MASTER_KEY_ID, B2_MASTER_KEY.

Is Backblaze B2 MCP Server maintained?

The last commit was 8 days ago (2026-09-14). The latest release is v0.2.1.