Agent-First HTTP

Persistent HTTP client for AI agents — one request, one JSON line.

Supported platforms: macOS, Linux, Windows.

Modes (single entrypoint):

• --mode cli (default)
• --mode pipe
• --mode curl

The key contract for agents is protocol determinism: stdout is always structured JSON, and failures are always structured {"code":"error",...} events with stable error_code values. No human-only text parsing, no mixed output channels, no ad-hoc error shapes.

CLI Mode

The default mode — one request, one JSON response, exit:

afhttp GET https://api.example.com/users
# {"code":"response","status":200,"body":[...],"trace":{"duration_ms":120,...}}

afhttp POST https://api.example.com/users --body '{"name":"Alice","email":"alice@example.com"}'
# {"code":"response","status":201,"body":{"id":42},...}

afhttp GET https://api.example.com/data --header "Authorization: Bearer sk-xxx"
# {"code":"response","status":200,...}

Structured error output examples:

{"code":"error","error_code":"connect_timeout","error":"request timed out after 30s","retryable":true,"trace":{"duration_ms":30012}}

{"code":"error","error_code":"invalid_request","error":"invalid --output format 'xml': expected json, yaml, or plain","retryable":false,"trace":{"duration_ms":0}}

Pipe Mode

For long-lived sessions with connection reuse, concurrent requests, and WebSocket — use afhttp --mode pipe:

afhttp --mode pipe <<'EOF'
{"code":"config","host_defaults":{"api.example.com":{"headers":{"x-api-key":"sk-xxx","api-version":"2023-06-01"}}}}
{"code":"request","id":"models","method":"GET","url":"https://api.example.com/v1/models"}
{"code":"request","id":"usage","method":"GET","url":"https://api.example.com/v1/usage"}
{"code":"request","id":"chat","method":"POST","url":"https://api.example.com/v1/messages","body":{"model":"general-chat-model","max_tokens":256,"messages":[{"role":"user","content":"Hello"}],"stream":true},"options":{"chunked":true,"chunked_delimiter":"\n\n"}}
EOF

output:

{"code":"config","host_defaults":{"api.example.com":{"headers":{"x-api-key":"[redacted]","api-version":"2023-06-01"}}},...}
{"code":"response","id":"models","status":200,"body":{"data":[{"id":"general-chat-model",...}]},"trace":{"duration_ms":92,"http_version":"h2","redirects":0,"remote_addr":"13.32.4.10"}}
{"code":"response","id":"usage","status":403,"body":{"error":{"type":"permission_error","message":"Your API key does not have permission"}},"trace":{"duration_ms":87,"http_version":"h2","redirects":0}}
{"code":"chunk_start","id":"chat","status":200,"headers":{"content-type":"text/event-stream"}}
{"code":"chunk_data","id":"chat","data":"event: content_block_delta\ndata: {\"delta\":{\"text\":\"Hello\"}}"}
{"code":"chunk_data","id":"chat","data":"event: content_block_delta\ndata: {\"delta\":{\"text\":\" there\"}}"}
{"code":"chunk_data","id":"chat","data":"event: message_stop\ndata: {}"}
{"code":"chunk_end","id":"chat","trace":{"duration_ms":834,"chunks":8}}

What just happened:

• One bash call — the heredoc sends all requests into one afhttp process; afhttp exits when stdin closes
• Auth set once per host — host_defaults applies auth only to matching host; credentials do not leak to other domains
• Three requests fired without waiting — models, usage, and chat all in-flight simultaneously
• Connection reuse is automatic — requests to the same host can reuse pooled connections without extra agent logic
• Out-of-order responses — usage arrived before chat finished; the agent matches by id
• Streaming inline — chat delivers events as they arrive, no buffering, no special setup
• HTTP errors are data — usage returned 403; afhttp delivers it as code: "response" with status: 403; the agent checks status, not exception types or text patterns

curl Compatibility

Use explicit curl mode. afhttp understands a subset of curl flags and returns structured JSON:

afhttp --mode curl -X POST https://api.example.com/users \
  -H "Authorization: Bearer sk-xxx" \
  -d '{"name":"Alice"}'
# {"code":"response","status":201,"body":{"id":42},...}

Install

macOS / Linux — Homebrew

brew install cmnspore/tap/afhttp

Windows — Scoop

scoop bucket add cmnspore https://github.com/cmnspore/scoop-bucket
scoop install afhttp

Any platform — Cargo

cargo install agent-first-http

Docs

• CLI — Generated CLI guide and flag reference from src/cli.rs
• Protocol Reference — full field specification
• Testing Strategy — layered tests, coverage gate, regression policy
• Design — architecture and principles

License

MIT