Data: Anthropic CLI

Anthropic CLI (ant)

The ant CLI exposes every Claude API resource as a shell subcommand. Compared to curl: request bodies are built from typed flags or piped YAML instead of hand-written JSON, @path inlines file contents into any string field, --transform extracts fields with a GJSON path (no jq), list endpoints auto-paginate (cap total results with --max-items N; --limit only sets the server page size), and the beta: prefix auto-sets the right anthropic-beta header.

When to use the CLI vs the SDK

CLI for the control plane, SDK for the data plane. Agents and environments are relatively static resources you define, configure, and debug with ant — check the YAML into your repo, apply from CI, inspect from a terminal. Sessions are dynamic and driven by your application through the SDK — create per task, stream events, react to tool calls, integrate into your product. Both hit the same API; the split is about where the call lives, not what’s possible.

	Control plane → ant	Data plane → SDK
Resources	agents, environments, skills, vaults, files	sessions, events
Cadence	Once per deploy / ad-hoc	Every task / every turn
Lives in	*.yaml in your repo + CI + terminal	Application code
Typical calls	create < agent.yaml, update --version N, list, retrieve, archive, --debug	sessions.create(), events.stream(), events.send()

Install and auth

# macOS
brew install anthropics/tap/ant
xattr -d com.apple.quarantine "$(brew --prefix)/bin/ant"

# Linux / WSL — pick the release from github.com/anthropics/anthropic-cli/releases
curl -fsSL "https://github.com/anthropics/anthropic-cli/releases/download/v${VERSION}/ant_${VERSION}_$(uname -s | tr A-Z a-z)_$(uname -m | sed -e s/x86_64/amd64/ -e s/aarch64/arm64/).tar.gz" \
  | sudo tar -xz -C /usr/local/bin ant

# Or from source (Go 1.22+)
go install github.com/anthropics/anthropic-cli/cmd/ant@latest

Auth is ANTHROPIC_API_KEY from the environment. Override the host with ANTHROPIC_BASE_URL or --base-url.

Command structure

ant <resource>[:<subresource>] <action> [flags]

Beta resources (agents, sessions, environments, deployments, skills, vaults, memory stores) live under beta: — the CLI auto-sends the right anthropic-beta header, so don’t pass it yourself unless overriding with --beta <header>.

ant models list
ant messages create --model {{OPUS_ID}} --max-tokens 1024 --message '{role: user, content: "Hello"}'
ant beta:agents retrieve --agent-id agent_01...
ant beta:sessions:events list --session-id session_01...

ant --help lists resources; append --help to any subcommand for its flags.

Global flags

Flag	Purpose
--format	auto (default: pretty if TTY, compact if piped), json, jsonl, yaml, pretty, raw, explore (interactive TUI)
--transform	GJSON path applied to the response (per-item on list endpoints). Not applied when --format raw.
-r, --raw-output	If the transformed result is a string, print it without quotes (jq semantics). Pair with --transform for scalar capture.
--max-items	Cap total results returned from auto-paginating list endpoints (distinct from --limit, which is the server page size).
--format-error / --transform-error	Same as --format/--transform, applied to error responses. -r does not apply to the error path — use --format-error yaml for unquoted error scalars.
--base-url	Override API host
--debug	Print full HTTP request + response to stderr (API key redacted)

Output — --transform + --format

--transform takes a GJSON path. On list endpoints it runs per item, not on the envelope.

ant beta:agents list --transform '{id,name,model}' --format jsonl

Extract a scalar for shell use: pair --transform with -r (--raw-output — prints strings unquoted, jq-style):

AGENT_ID=$(ant beta:agents create --name "My Agent" --model '{id: {{SONNET_ID}}}' \
  --transform id -r)

Input — flags, stdin, @file

Flags — scalar fields map directly. Structured fields accept relaxed-YAML syntax (unquoted keys) or strict JSON. Repeatable flags build arrays (each --tool, --event, --message appends one element):

ant beta:agents create \
  --name "Research Agent" \
  --model '{id: {{OPUS_ID}}}' \
  --tool '{type: agent_toolset_20260401}' \
  --tool '{type: custom, name: search_docs, input_schema: {type: object, properties: {query: {type: string}}}}'

Stdin — pipe a full JSON or YAML body. Merged with flags; flags win on conflict (for array fields, any flag replaces the stdin array entirely — it does not append). Quote the heredoc delimiter (<<'YAML') to disable shell expansion inside the body:

ant beta:agents create <<'YAML'
name: Research Agent
model: {{OPUS_ID}}
system: |
  You are a research assistant. Cite sources for every claim.
tools:
  - type: agent_toolset_20260401
YAML

@file references — inline a file’s contents into any string-valued field. Inside structured flag values, quote the path. Binary files are auto-base64’d; force with @file:// (text) or @data:// (base64). Escape a literal leading @ as \@.

ant beta:agents create --name "Researcher" --model '{id: {{SONNET_ID}}}' --system @./prompts/researcher.txt

ant messages create --model {{OPUS_ID}} --max-tokens 1024 \
  --message '{role: user, content: [
    {type: document, source: {type: base64, media_type: application/pdf, data: "@./scan.pdf"}},
    {type: text, text: "Extract the text from this scanned document."}
  ]}' \
  --transform 'content.0.text' -r

Flags that natively take a file path (e.g. --file on beta:files upload) accept a bare path without @.

Version-controlled Managed Agents resources

This is the recommended flow for defining agents and environments — check the YAML into your repo and sync via create (first time) / update (thereafter). See shared/managed-agents-core.md for the field reference.

# summarizer.agent.yaml
name: Summarizer
model: {{SONNET_ID}}
system: |
  You are a helpful assistant that writes concise summaries.
tools:
  - type: agent_toolset_20260401

# Create (once) — capture the ID
AGENT_ID=$(ant beta:agents create < summarizer.agent.yaml --transform id -r)

# Update (CI) — needs ID + current version (optimistic lock)
ant beta:agents update --agent-id "$AGENT_ID" --version 1 < summarizer.agent.yaml

Same pattern for environments (ant beta:environments create|update < env.yaml), then start a session with both IDs:

ant beta:sessions create --agent "$AGENT_ID" --environment-id "$ENV_ID" --title "Task"
ant beta:sessions:events send --session-id "$SID" \
  --event '{type: user.message, content: [{type: text, text: "Summarize X"}]}'
ant beta:sessions:events list --session-id "$SID" --transform 'content.0.text' -r
ant beta:sessions:events stream --session-id "$SID"   # live event stream

Interactive session loop (stream-before-send)

ant beta:sessions:events stream only delivers events emitted after the stream opens — so open it before sending the kickoff to avoid missing early events. Use process substitution to hold the stream on a file descriptor, send, then read:

exec {stream}< <(ant beta:sessions:events stream --session-id "$SID" \
  --transform '{type,text:content.#(type=="text").text,err:error.message}' --format yaml)

ant beta:sessions:events send --session-id "$SID" > /dev/null <<'YAML'
events:
  - type: user.message
    content:
      - type: text
        text: Summarize the repo README
YAML

type=
while IFS= read -r -u "$stream" line; do
  case "$line" in
    type:\ session.status_idle) break ;;
    type:\ session.error)
      IFS= read -r -u "$stream" next || next=
      case "$next" in err:\ *) msg=${next#err: } ;; *) msg=unknown ;; esac
      printf '\
[Error: %s]\
' "$msg"; break ;;
    type:\ *) type=${line#type: } ;;
    text:*)
      [[ $type == agent.message ]] || continue
      val=${line#text: }
      case "$val" in '|-'|'|') ;; *) printf '%s' "$val" ;; esac ;;
    \ \ *)
      if [[ $type == agent.message ]]; then printf '%s\
' "${line#  }"; fi ;;
  esac
done
exec {stream}<&-

This works for interactive exploration and demos. For application code that needs to react to agent.tool_use / agent.custom_tool_use events, reconnect after drops, or dedup against events.list, use the SDK — see shared/managed-agents-client-patterns.md.

Scripting patterns

--transform id -r on a list endpoint emits one bare ID per line — compose with xargs, or use --max-items N to bound the result set without piping through head:

FIRST=$(ant beta:agents list --transform id -r --max-items 1)
ant beta:agents:versions list --agent-id "$FIRST" --transform '{version,created_at}' --format jsonl

Error shaping mirrors the success path (note: -r does not apply to error output — use --format-error yaml for an unquoted scalar here):

ant beta:agents retrieve --agent-id bogus --transform-error error.message --format-error yaml 2>&1

Shell completion: ant @completion {zsh|bash|fish|powershell}.

For the full, always-current reference (including per-endpoint flags), WebFetch the Anthropic CLI URL in shared/live-sources.md.