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Apple Foundation Models CLI (fm)

fm is a command line interface (/usr/bin/fm, ships with macOS) to Apple's on-device Foundation Model. Everything runs locally, so there is no API key and no network call.

Key Points / Features​

  • Single model: system (on-device Apple Foundation Model, the default)
  • fm available checks that the model is available on the machine
  • fm respond is a one-shot prompt; it streams by default and accepts stdin
  • fm chat is an interactive session; sessions are saved to ~/.fm/sessions/
  • fm serve starts a Chat Completions API server (OpenAI-style)
  • fm schema generates a JSON schema for structured output
  • fm count-tokens counts tokens for a prompt, instructions or a saved transcript (on-device model only)
  • fm license shows and accepts the Legal Notice & Terms

Commands​

CommandPurpose
availableCheck model availability
chatInteractive chat session
count-tokensCount tokens in a prompt or instructions
licenseShow and agree to the Legal Notice & Terms
respondGenerate a response to a prompt
schemaGenerate a structured output generation schema
serveStart a Chat Completions API server

respond​

fm respond 'What is Swift?'
fm respond --use-case content-tagging 'Analyze this text'
fm respond --image photo.jpg --text 'What is in this image?'
echo 'What is Swift?' | fm respond

Useful options:

  • -i, --instructions <text>: system-style instructions
  • --schema <file>: constrain output to a structured output schema
  • --tool <name>: enable a built-in tool (barcode, ocr; repeatable)
  • --image <path> with --label <name>: multimodal input
  • --save-transcript <file> / --resume <file>: persist and continue a conversation
  • --use-case <general|content-tagging> and --guardrails <default|permissive-content-transformations>
  • -g, --greedy: greedy sampling (deterministic); --[no-]stream

Structured output​

fm schema object --name Person --string name --int age > person.json
fm respond --schema person.json 'Alice is 30 years old'

The generated schema is plain JSON schema (type: object, properties, required, x-order).

serve​

fm serve --port 1976
fm serve --socket /tmp/fm.sock   # Unix domain socket, recommended for local Python bindings

Endpoints: GET /health, GET /v1/models, POST /v1/chat/completions (streaming and non-streaming). Because it speaks the Chat Completions format, existing OpenAI-compatible clients can point at it.

count-tokens​

fm count-tokens -q 'Hello world'            # bare integer
fm count-tokens -i 'Answer concisely' 'What is Swift?'
fm count-tokens --transcript session.json