OnlyCLI

OnlyCLI

[](https://github.com/onlycli/onlycli/actions/workflows/ci.yml) [](https://goreportcard.com/report/github.com/onlycli/onlycli) [](LICENSE)

Turn any OpenAPI spec into a complete CLI. One command. One binary. 35x fewer tokens than MCP.

Every endpoint in the GitHub REST API (1,107 operations) becomes a typed CLI command with flags, help text, and shell completion.

Install

go install github.com/onlycli/onlycli/cmd/onlycli@latest

Or download a pre-built binary from Releases.

Quick Start

# 1. Generate -- point at any OpenAPI 3.x spec (local file or URL)
onlycli generate \
  --spec https://raw.githubusercontent.com/swagger-api/swagger-petstore/master/src/main/resources/openapi.yaml \
  --name petstore --out ./petstore-cli

# 2. Build
cd petstore-cli && go mod tidy && go build -o petstore .

# 3. Use
./petstore pet find-pets-by-status --status available --format table
./petstore --help

That's it. Every operation in the spec is now a CLI command.

What You Get

Every generated CLI ships with:

| Capability | How | |---|---| | Every endpoint as a command | Grouped by tag, named by operationId | | All parameters as --flags | Path, query, header, and request body fields | | 7 output formats | --format json\|yaml\|table\|csv\|pretty\|jsonl\|raw | | Field projection | --transform "#.name" via GJSON | | Go template output | --template '{{.login}}' | | Auto-pagination | --page-limit N auto-detects Link, cursor, offset, page-number | | Streaming | --stream for SSE and NDJSON responses | | File input | --data @payload.json or --data @- for stdin | | OAuth2 authentication | Device flow (interactive) + client credentials (CI) | | Multi-profile config | config set staging.token xxx && --profile staging | | Retry with backoff | --max-retries 3 for transient 429/5xx errors | | Dry-run mode | --dry-run prints the request without sending | | HTTP/2 + gzip | Modern transport, automatic content decompression | | Shell completion | completion bash\|zsh\|fish\|powershell with enum hints | | Cross-platform | Linux, macOS, Windows; amd64, arm64 |

Examples

Pre-generated CLIs from live public specs:

| Example | Source Spec | Groups | Commands | |---|---|---|---| | [petstore](examples/petstore/) | Swagger Petstore | 3 | 19 | | [github](examples/github/) | GitHub REST API | 43 | 1,107 |

Regenerate them yourself:

make generate-example

Comparison

| | OnlyCLI | curl | Restish | MCP tools | |---|---|---|---|---| | Typed commands per endpoint | Yes | No | Yes | Varies | | Single distributable binary | Yes | Yes | Yes | No | | Output formatting (table/yaml/csv) | Yes | No | No | No | | Multi-scheme pagination | Yes | No | No | No | | Streaming (SSE/NDJSON) | Yes | Manual | No | Varies | | Works offline, no server process | Yes | Yes | Yes | No | | Token cost for AI agents | Low | Low | Low | High |

Detailed write-ups: vs Stainless · vs Restish · vs curl/HTTPie

For AI Agents: 35x Cheaper Than MCP

A GitHub MCP server loads 55,000 tokens into every prompt. Three services consume 72% of your context window on idle. At scale, that is $51,000/month in pure schema overhead.

OnlyCLI takes the opposite approach:

1. Generate a binary once from the spec
2. Agent calls ./cli --help to discover commands (~200 tokens)
3. Agent runs ./cli repos get --owner x --repo y and reads stdout

Stable command names, predictable flags, structured JSON output. No MCP server, no schema injection, no connection management. See the full cost analysis.

Development

git clone https://github.com/onlycli/onlycli.git && cd onlycli
make test          # unit + integration tests
make lint          # golangci-lint
make check         # fmt + vet + lint + test
make build         # build to bin/onlycli

See [CONTRIBUTING.md](CONTRIBUTING.md) for the full guide and [ARCHITECTURE.md](ARCHITECTURE.md) for codebase structure.

License

[MIT](LICENSE)

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: OnlyCLI
• Source: OnlyCLI/OnlyCLI
• License: MIT
• Homepage: https://onlycli.github.io/OnlyCLI/

Install and usage instructions live in the source repository linked above.