Yandex Object Storage: MCP, CLI and skill for Yandex Cloud S3
yandex-s3-mcp-ai-cli
One Go binary: an MCP server, CLI and skill for Yandex Cloud S3, read-only by default, with write and delete enabled by flags
- 0 ★ on the repository
- Last commit
Broad access
Why this level
- With write, delete and admin enabled the agent changes and erases objects and bucket policies, including versions and Object Lock
- A static Object Storage key gives access to cloud data, and its leak exposes backups
Install
- Works in
- Services
Manual install
yandex-s3 mcp install --client claude-code --scope userTake the binary from the releases or build it from the sources; first `yandex-s3 auth set`, then optionally `yandex-s3 skill install`. The command prints `claude mcp add`.
Access and checks
How we reviewBroad accessThe tool can change data, run commands or handle secrets.
- With write, delete and admin enabled the agent changes and erases objects and bucket policies, including versions and Object Lock
- A static Object Storage key gives access to cloud data, and its leak exposes backups
This is third-party code. Review the repository files before installing.
What it does
The `yandex-s3` Go binary combines an MCP server, a command line and a skill for Yandex Object Storage. The agent searches objects, views versions and restores backups: by default only read tools are registered (`s3_list_objects`, `s3_get_object`, `s3_list_object_versions`, `s3_presign_get`, `s3_prefix_usage` and others). Writing, deleting and bucket administration are enabled separately by the `--allow-write`, `--allow-delete`, `--allow-admin` flags or the `YANDEX_S3_ALLOW` variable. Dangerous operations go through confirmation under the `YANDEX_S3_DESTRUCTIVE_POLICY` policy. The `yandex-s3 mcp install --client cursor` command (or `claude-code`, `codex`, `claude-desktop`) writes the server into the client config without keys, and `yandex-s3 skill install` puts `SKILL.md` and six references into `~/.claude/skills/yandex-s3`.
Who it is for. Devops engineers and developers whose backups and files live in Yandex Object Storage and who need safe agent access to them.
Good fit when
- Before a restore you have to check a prefix contents and the versions of backup objects
- The agent needs read-only bucket access while writing and deleting stay closed
- You need to find the heaviest objects and see where bucket space goes
- You need temporary access to a file and the agent issues a presigned link for the needed period
Not a fit when
- You need other S3 stores: the server is tuned to the Yandex Object Storage profile
- You need a billing summary: counting size by prefix does not replace the cloud bill
- You need to enable deletion and writing quickly with no confirmations: the default gate requires consent
Example request
Show object versions in the backups/daily/ prefix and find the heaviest file without downloading anythingMCP
- Transport
- stdio
- Authentication
- API key
Environment variables
YANDEX_S3_ACCESS_KEY_IDrequired, secret- Object Storage static key id
YANDEX_S3_SECRET_ACCESS_KEYrequired, secret- Secret part of the static key
YANDEX_S3_POOL- Storage pool, ru-central1 by default
YANDEX_S3_ALLOW- Access levels: write, delete, admin comma-separated
Limitations
The project has development status: release 0.1.0 is published and the repository itself notes that the profile and cloud API still need live checking. It works with one default pool, `ru-central1`, and needs an Object Storage access key and secret. If the service does not support conditional writes, writing without overwrite is blocked before any S3 call and move is disabled. Inline read and write are capped at 262,144 bytes, and large files go through presigned links or the `FILE_ROOT` folder. Analytic scans read at most 10,000 objects and do not replace billing. Zero stars, last commit in October 2026.
How to disable. Remove the server from the client config (the installer keeps a `.bak` file), erase `~/.config/yandex-s3/credentials` and the skill in `~/.claude/skills/yandex-s3`, and revoke the access key in the Yandex Cloud console.
FAQ
Can the agent delete objects?
Not by default: only read tools are registered. Deletion is enabled with `--allow-delete`, and every action goes through confirmation.
Where are the keys stored?
In the `~/.config/yandex-s3/credentials` file with 0600 permissions or in the `YANDEX_S3_ACCESS_KEY_ID` and `YANDEX_S3_SECRET_ACCESS_KEY` variables. They are not written to the client config.
How do I connect it to Cursor or Codex?
With `yandex-s3 mcp install --client cursor` or `--client codex`; add `--dry-run` to check first. Cursor also has an install button using the Docker image.
What does skill install do?
It puts `SKILL.md` and six references (backup and restore, sharing, least privilege, cost hygiene, migration, incident response) into `~/.claude/skills/yandex-s3`.
Is there a settings health check?
The `yandex-s3 doctor` command checks key source and permissions, DNS, TLS and clock skew: over five minutes gives a warning, over fifteen an error.
Discussion
No questions or reviews yet.
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README in short
The README in Russian and English covers a quick start with the binary and `auth set`, connection to Claude Code, Cursor and Codex, a tool table by access level, CLI commands, skill installation, the confirmation policy for dangerous operations and a backup version check scenario.