S3 MCP Connector

🪣 s3-mcp-connector

Talk to Amazon S3 — or LocalStack, MinIO, any S3-compatible store — from an MCP-speaking agent.

---

A single static Go binary that speaks the Model Context Protocol and exposes 8 tools for working with S3: list buckets, list/read/write/delete objects, create/delete buckets. Point it at real AWS or at a local LocalStack/MinIO instance with one environment variable — same binary, same tools, zero code changes.

No Python, no uv, no runtime dependency to install — just a binary and an .mcp.json.

✨ Why this exists

An agent that can only *talk about* your S3 buckets isn't that useful.

This gives it hands: it can look inside a bucket, read a config file out

of it, drop a report back in, or clean up a stale prefix — safely, with

guardrails on size and destructive actions built in.

🧰 Tools

Every tool accepts an optional response_format: markdown (default, pretty tables for a chat UI) or json (for programmatic use).

s3_get_object auto-detects text vs. binary content and caps output at 200,000 bytes by default (raise via max_bytes, hard cap 5,000,000) — it's built for reading configs, logs, and small data files, not bulk transfer. Reach for the AWS CLI or SDK directly for large objects.

🚀 Quickstart

Fastest path: grab a prebuilt bundle from the latest release — download s3-mcp-connector-plugin- - - .zip, unzip it, and point Cowork/Claude at the plugin/ folder inside (see step 4 of SETUP.md). No Go toolchain required.

From source:

# 1. Build

cd go-server go mod tidy go build -o s3-connector-server . cp s3-connector-server ../plugin/servers/go/

2. Spin up LocalStack to test against (no AWS account needed)

cd .. docker compose up -d

3. Point the connector at it

export AWS_ACCESS_KEY_ID=test export AWS_SECRET_ACCESS_KEY=test export AWS_REGION=us-east-1 export S3_ENDPOINT_URL=http://localhost:4566 export S3_FORCE_PATH_STYLE=true

./go-server/s3-connector-server # serves MCP over stdio

Or make build && make localstack-up — see the Makefile for every shortcut (test, vet, fmt, lint, tidy, localstack-down).

Full walkthrough — including wiring this up as a Claude/Cowork plugin and switching from LocalStack to real AWS — is in [SETUP.md](SETUP.md).

🔐 Configuration

Everything is environment variables, passed through by the plugin's .mcp.json:

🧪 Quality bar

This isn't a toy script — it's got the same checks you'd expect from a production Go service:

• ✅ Unit tests for every input-validation path (go test ./...)
• ✅ `go vet` + `gofmt` clean
• ✅ [golangci-lint](https://golangci-lint.run/) (govet, staticcheck, errcheck, gosec, and more)
• ✅ [govulncheck](https://go.dev/blog/vuln) — no known vulnerabilities in the dependency graph
• ✅ [CodeQL](https://codeql.github.com/) static security analysis on every push
• ✅ End-to-end verified against real LocalStack — every tool (create/delete bucket, put/get/head/list/delete object, and the 404 error path) was exercised against a live S3-compatible service, not mocks
• ✅ [Dependabot](.github/dependabot.yml) keeps Go modules and Actions current

All of it runs in CI on every push and PR.

🏷️ Releases & versioning

Versions follow semver and are cut automatically by release-please from Conventional Commits on main:

• fix: ... → patch (v0.1.0 → v0.1.1)
• feat: ... → minor (v0.1.1 → v0.2.0)
• feat!: ... / BREAKING CHANGE: footer → major (v0.2.0 → v1.0.0)

Every merged PR updates a standing "chore(main): release vX.Y.Z" PR with an auto-generated CHANGELOG.md. Merging that PR:

1. tags the release and publishes it on GitHub
2. builds and attaches zipped, ready-to-install plugin bundles for linux/darwin/windows × amd64/arm64
3. regenerates server.json from those exact assets (fresh version + SHA-256 hashes) and publishes it to the official MCP Registry via mcp-publisher, authenticated with GitHub OIDC — no stored secrets

See .github/workflows/release-please.yml and .github/workflows/publish-mcp-registry.yml (also runnable by hand for an existing tag via workflow_dispatch).

📁 Layout

s3-mcp-connector/

├── README.md ← you are here ├── SETUP.md ← step-by-step setup guide (LocalStack + real AWS) ├── CONTRIBUTING.md ← how to contribute ├── CODE_OF_CONDUCT.md ├── SECURITY.md ← vulnerability reporting ├── CODEOWNERS ├── LICENSE ← MIT ├── Makefile ← build / test / lint / localstack shortcuts ├── docker-compose.yml ← LocalStack, for local testing ├── .golangci.yml ← lint rules ├── release-please-config.json ← semver/changelog automation config ├── .release-please-manifest.json ├── server.json ← MCP Registry manifest (regenerated fresh per release by CI) ├── scripts/ │ └── render-server-json.sh ← rebuilds server.json from a release's zip assets ├── .github/ │ ├── workflows/ │ │ ├── ci.yml ← build, vet, test, lint, govulncheck │ │ ├── codeql.yml ← security scanning │ │ ├── pr-title.yml ← Conventional Commits PR title check │ │ ├── release-please.yml ← version PRs, tagging, GitHub releases │ │ ├── publish-mcp-registry.yml ← publishes server.json to the MCP Registry │ │ └── rebuild-release-assets.yml ← manual re-attach fallback │ ├── ISSUE_TEMPLATE/ │ ├── PULL_REQUEST_TEMPLATE.md │ └── dependabot.yml ├── go-server/ ← the MCP server source │ ├── main.go │ ├── main_test.go │ ├── go.mod / go.sum │ └── README.md └── plugin/ ← installable Cowork/Claude plugin ├── .claude-plugin/plugin.json ├── .mcp.json ← holds credentials locally — never commit real ones └── servers/go/ ← compiled binary goes here

🤝 Contributing

PRs and issues are very welcome — see [CONTRIBUTING.md](CONTRIBUTING.md) for the full guide (setup, coding conventions, how to add a new tool) and the [Code of Conduct](CODE_OF_CONDUCT.md).

main is protected: every change, including the maintainer's, lands via pull request with CI green. PR titles must follow Conventional Commits — that's what drives the automatic versioning above.

Found a security issue? Please follow [SECURITY.md](SECURITY.md) instead of opening a public issue.

📄 License

MIT © Ferhat Dundar