examples · v0.2

In
practice.

Fourteen demonstrations of Machine Mode on the wire. The standard, made concrete — sources, transformers, and sinks.

Each demonstration shows a real conforming tool — usually called outline — exercising one piece of the standard. The first arrives as a streamed JSONL output, one line at a time, the way a consumer actually reads it. The rest are static for scanning.

Every conforming tool plays one of three pipeline roles — a source that emits JSONL, a transformer that reads JSONL and emits JSONL, or a sink that reads JSONL and performs side effects. Demos § 01 – § 12 show sources. § 13 shows a transformer in isolation. § 14 shows a sink. The shell ecosystem we lean on (jq, tee, pipefail) already speaks JSONL; no new toolchain.

Live · search with limit and cursorstreaming · revealed as the tool would emit it

§ 01

Discoverable

Discover what a tool can do.

A consumer can learn what a tool exposes without invoking it, without credentials, and without network access. The schema and capability commands return one JSON object — discovery metadata, not a JSONL stream.

01$ outline schema --output json --command search
02{"$schema":"https://json-schema.org/draft/2020-12/schema","title":"Outline search event","type":"object","required":["type"],"properties":{"type":{"enum":["aoi:meta","hit","aoi:warning","aoi:error","aoi:summary"]}}}
03$ 
04$ outline capabilities --output json
05{"tool":"outline","tool_version":"1.8.2","aoi_versions":["0.2"],"schemas":[{"name":"com.example.outline.events","versions":["1.0.0"],"default":"1.0.0"}],"commands":[{"name":"search","read_only":true,"bounded":true,"supports_cursor":true,"event_types":["aoi:meta","hit","aoi:summary"]},{"name":"delete","read_only":false,"destructive":true,"requires_confirm":true,"supports_dry_run":true,"supports_idempotency_key":true}]}

Schema discovery · returns a single JSON object

No credentials. No network. No business query.
capabilities is one JSON object so it can be parsed in a single read.
The destructive flag on delete tells a planner this command demands extra ceremony.

§ 02

StreamableBounded

Bounded, streamed search.

Every read declares its appetite. Results arrive incrementally as the tool produces them. When more exists, the terminal summary says so — and hands back a cursor so the consumer can continue.

01$ outline search "agent operable" --output jsonl --limit 50
02{"type":"aoi:meta","tool":"outline","tool_version":"1.8.2","aoi_version":"0.2","schema_name":"com.example.outline.events","schema_version":"1.0.0","command":"search"}
03{"type":"hit","rank":1,"id":"doc_91","title":"Agent-operable interfaces","snippet":"A conforming tool exposes…"}
04{"type":"hit","rank":2,"id":"doc_177","title":"Why machine mode","snippet":"Today's tools were built for humans…"}
05…
06{"type":"hit","rank":50,"id":"doc_2041","title":"Adopt AOI-CLI","snippet":"The conformance contract is small…"}
07{"type":"aoi:summary","ok":true,"count":50,"truncated":true,"next_cursor":"opaque-token-abc123","elapsed_ms":612}

Bounded streaming search — exit 0, truncated, with continuation

The consumer chose the limit; the tool honored it.
truncated:true means more results exist beyond this page.
next_cursor is opaque — the tool defines it.

§ 03

BoundedComposable

Continue from a cursor.

Pagination is part of the contract, not a per-tool ad-hoc. The cursor you got from one call goes back as the cursor on the next call. The state lives with the consumer.

01$ outline search "agent operable" --output jsonl --limit 50 --cursor opaque-token-abc123
02{"type":"aoi:meta","tool":"outline","aoi_version":"0.2","schema_version":"1.0.0","command":"search"}
03{"type":"hit","rank":51,"id":"doc_2110","title":"…"}
04…
05{"type":"hit","rank":83,"id":"doc_3441","title":"…"}
06{"type":"aoi:summary","ok":true,"count":33,"truncated":false,"next_cursor":null,"elapsed_ms":410}

Following the cursor returned in §02

truncated:false + next_cursor:null marks the end of the result set.
A consumer never needs to invent its own pagination.

§ 04

Safe

Dry-run before any write.

Before a destructive operation runs, --dry-run emits plan events: this is what would happen. Zero side effects. The plan is the contract.

01$ outline delete --where "stale=true" --dry-run --output jsonl
02{"type":"aoi:meta","tool":"outline","command":"delete","dry_run":true}
03{"type":"aoi:plan","action":"delete","target":"doc_44","title":"Old onboarding draft"}
04{"type":"aoi:plan","action":"delete","target":"doc_91","title":"2024-Q4 plan archive"}
05{"type":"aoi:plan","action":"delete","target":"doc_133","title":"Deprecated docs index"}
06{"type":"aoi:summary","ok":true,"would_affect":3,"executed":false}

A delete that would touch 3 documents — but does not

executed:false makes the no-op explicit; a wrapper can assert on it.
Plan events are typed the same way the real apply events would be.

§ 05

SafeAuditable

Confirmed destructive apply.

The real run requires --confirm. Bulk operations demand --confirm-count N as a guard against an unexpected blast radius. Every actual side effect produces a structured record.

01$ outline delete --where "stale=true" --output jsonl --confirm --confirm-count 3
02{"type":"aoi:meta","tool":"outline","command":"delete"}
03{"type":"deleted","target":"doc_44","at":"2026-05-24T17:42:11Z","actor":"kevin"}
04{"type":"deleted","target":"doc_91","at":"2026-05-24T17:42:11Z","actor":"kevin"}
05{"type":"deleted","target":"doc_133","at":"2026-05-24T17:42:11Z","actor":"kevin"}
06{"type":"aoi:summary","ok":true,"count":3,"executed":true,"elapsed_ms":204}

Same query as §04, now committed — count guard matches

If --confirm-count had been 4, the tool would have refused without touching anything.
deleted events carry stable IDs — a downstream audit log can ingest them as-is.

§ 06

Idempotent

Idempotent writes.

The same write attempted twice — same outcome, no duplicate. The idempotency key lets the tool recognize a retry and return the prior result instead of doubling the effect.

01$ outline create-doc --title "Release notes" --idempotency-key rel-2026-05 --output jsonl
02{"type":"aoi:meta","command":"create-doc"}
03{"type":"created","id":"doc_9001","title":"Release notes","idempotency_key":"rel-2026-05","duplicate":false}
04{"type":"aoi:summary","ok":true,"count":1,"executed":true}
05$ 
06$ outline create-doc --title "Release notes" --idempotency-key rel-2026-05 --output jsonl
07{"type":"aoi:meta","command":"create-doc"}
08{"type":"created","id":"doc_9001","title":"Release notes","idempotency_key":"rel-2026-05","duplicate":true}
09{"type":"aoi:summary","ok":true,"count":1,"executed":false}

Two invocations, same key — second is a safe replay

Both runs return the same id and exit 0.
duplicate:true on the second is the explicit signal — the consumer can rely on the field, not infer from elapsed time.

§ 07

VerifiableDiscoverable

Doctor — readiness as a stream.

Tools surface their own health: config, dependencies, credentials, connectivity. Each check is a typed event. The summary aggregates.

01$ outline doctor --output jsonl
02{"type":"aoi:meta","tool":"outline","command":"doctor"}
03{"type":"aoi:check","name":"config_file","ok":true,"severity":"info","detail":"~/.outline.toml"}
04{"type":"aoi:check","name":"api_token","ok":true,"severity":"info","detail":"sourced from OUTLINE_TOKEN"}
05{"type":"aoi:check","name":"endpoint_reachable","ok":false,"severity":"error","detail":"connect ETIMEDOUT api.outline.example"}
06{"type":"aoi:summary","ok":false,"count":3,"error_count":1}

Multiple typed checks · process exits non-zero when any check fails

Each check has the same envelope — easy for a monitoring agent to roll up.
summary.ok=false with non-zero exit makes the failure unambiguous.

§ 08

Streamable

Watch — an unbounded stream.

Some operations don't have a natural end. The tool documents that the stream is unbounded, optionally emits heartbeats so a consumer can distinguish quiet from dead, and produces a summary only on cancellation.

01$ outline watch --output jsonl
02{"type":"aoi:meta","tool":"outline","command":"watch","unbounded":true}
03{"type":"entry","change":"created","id":"doc_42","at":"2026-05-24T17:48:10Z"}
04{"type":"entry","change":"updated","id":"doc_42","at":"2026-05-24T17:49:23Z"}
05{"type":"aoi:heartbeat","at":"2026-05-24T17:50:00Z"}
06{"type":"aoi:heartbeat","at":"2026-05-24T17:51:00Z"}
07{"type":"entry","change":"deleted","id":"doc_19","at":"2026-05-24T17:51:42Z"}
08⌃C
09{"type":"aoi:summary","ok":false,"reason":"interrupted","partial":true,"count":3}

Subscription stream with periodic heartbeats

unbounded:true on meta tells the consumer not to wait for natural completion.
Heartbeats let a supervisor distinguish a quiet stream from a dead one without TCP keepalive.
A graceful interrupt still produces a structured summary.

§ 09

Composable

Compose tools in a pipeline.

The output of one Machine Mode tool is the input of the next, by construction. Each tool emits its own meta and summary; consumers ignore unknown event types unless explicitly configured to fail.

01$ outline search "agent" --output jsonl --limit 20 \
02$   | summarize --input-jsonl - --output jsonl \
03$   | tee run.jsonl \
04$   | jq -e 'select(.type=="aoi:summary") | .ok == true'
05{"type":"aoi:meta","tool":"outline","command":"search"}
06{"type":"aoi:meta","tool":"summarize","input_schemas":["com.example.outline.events@1.0.0"]}
07{"type":"abstract","source_id":"doc_91","text":"A typed interface…"}
08…
09{"type":"aoi:summary","ok":true,"tool":"outline","count":20}
10{"type":"aoi:summary","ok":true,"tool":"summarize","count":20}

Search → summarize → terminal · pipefail keeps the whole chain honest

Both producer and consumer emit their own summary — no information is lost in the pipe.
jq -e on the terminal summary turns Machine Mode into a shell-level boolean.
With set -o pipefail, an upstream failure short-circuits the whole pipeline.

§ 10

Versioned

Negotiate a schema version.

A tool can ship more than one version of its event schema from a single binary. Consumers pin to what they support; the tool honors and reports.

01$ outline search "agent" --output jsonl --schema-version 1 --limit 1
02{"type":"aoi:meta","tool":"outline","schema_name":"com.example.outline.events","schema_version":"1.0.0"}
03{"type":"hit","rank":1,"id":"doc_91","title":"Agent-operable"}
04{"type":"aoi:summary","ok":true,"count":1}
05$ 
06$ outline search "agent" --output jsonl --schema-version 2 --limit 1
07{"type":"aoi:meta","tool":"outline","schema_name":"com.example.outline.events","schema_version":"2.0.0"}
08{"type":"hit","rank":1,"document":{"id":"doc_91","title":"Agent-operable","mime":"text/markdown"}}
09{"type":"aoi:summary","ok":true,"count":1}

Two consumers, same tool, different schemas — both valid

v2 nested the result in a document object — a breaking shape change, so it got a major bump.
A consumer that depends on v1 keeps working; one that wants v2 opts in explicitly.

§ 11

Verifiable

Errors carry their own retry semantics.

An error event includes category and retryable as portable fields. A consumer can build retry logic that works across every conforming tool without learning each tool's bespoke codes.

01$ outline create-doc --title "…" --output jsonl
02{"type":"aoi:meta","command":"create-doc"}
03{"type":"aoi:error","code":"RATE_LIMITED","category":"rate_limited","message":"60 writes per minute exceeded","retryable":true,"retry_after_ms":7200}
04{"type":"aoi:summary","ok":false,"error_count":1,"executed":false}

Rate-limit error with hint · retry is a contract, not a guess

category=rate_limited is from the standard taxonomy; the consumer's retry policy knows what to do without reading docs.
retry_after_ms is the tool's hint — the consumer is free to use it or implement its own backoff.

§ 12

Verifiable

The terminal summary is the success signal.

Exit 0 means "the process finished." Success means "the work completed and was reported." Without the terminal summary, EOF is the cross-language crash signal — even when exit code is 0.

01$ # Healthy run — exit 0, summary present, ok=true
02{"type":"aoi:meta","command":"search"}
03{"type":"hit","rank":1,"id":"doc_1"}
04{"type":"aoi:summary","ok":true,"count":1}
05echo $?  # 0
06$ 
07$ # Crash mid-stream — exit 0 because Bun's default handler swallowed it
08{"type":"aoi:meta","command":"search"}
09{"type":"hit","rank":1,"id":"doc_1"}
10# <EOF, no summary, exit 0>
11echo $?  # 0  — but consumer MUST treat this as failure

Same exit code, different truths — only the summary is authoritative

A consumer that trusts exit code alone will silently accept the truncated stream as success.
The terminal summary is the only honest success signal — and its absence is the only honest crash signal.

§ 13

Composable

A transformer in isolation.

A transformer reads upstream AOI events on stdin, dispatches on event.type, and emits its own typed events. Same envelope rules apply — meta opens, summary terminates. Domain events get transformed; control events (warning, error, summary) get acknowledged and propagated.

01$ outline search "agent operable" --output jsonl --limit 3 | summarize --input-jsonl - --output jsonl --max-tokens 60
02{"type":"aoi:meta","tool":"summarize","tool_version":"0.4.1","aoi_version":"0.2","schema_name":"com.example.summarize.events","schema_version":"1.0.0","command":"summarize","input_schemas":["com.example.outline.events@1.0.0"]}
03{"type":"abstract","source_id":"doc_91","text":"A typed interface a non-human can rely on — discoverable, bounded, safe."}
04{"type":"abstract","source_id":"doc_177","text":"Today's tools were built for humans; agents need something safer than scraped terminal text."}
05{"type":"abstract","source_id":"doc_2041","text":"Conformance is small: emit JSONL, expose a schema, terminate on a summary."}
06{"type":"aoi:summary","ok":true,"count":3,"input_count":3,"warning_count":0,"error_count":0,"elapsed_ms":380}

summarize reads hit events from an upstream source, emits abstract events

input_schemas in meta declares what upstream shapes the transformer accepts — a downstream tool can verify the chain is type-compatible.
source_id preserves the upstream identity so a consumer can re-correlate transformed events back to the originals.
Unknown upstream event types are ignored silently unless --fail-on-unknown is set.
Upstream error events propagate: summary.ok becomes false unless --continue-on-error is passed.

§ 14

AuditableComposableSafe

A sink.

A sink reads JSONL on stdin and performs side effects. Its output stream is mostly the audit trail — what got created, updated, or sent — plus the meta and summary envelopes every conforming tool emits. A sink can be the end of an AOI pipeline.

01$ cat exports.jsonl | outline import --input-jsonl - --output jsonl --confirm
02{"type":"aoi:meta","tool":"outline","command":"import","input_mode":"jsonl","input_schemas":["com.example.export.events@1.0.0"]}
03{"type":"created","target":"doc_9001","title":"Q4 retrospective","source_id":"export_44","at":"2026-05-24T18:11:02Z"}
04{"type":"created","target":"doc_9002","title":"Postmortem template","source_id":"export_45","at":"2026-05-24T18:11:03Z"}
05{"type":"aoi:error","category":"validation","code":"INPUT_JSONL_PARSE_ERROR","line_number":7,"message":"Invalid JSON on input line 7","retryable":false}
06{"type":"aoi:summary","ok":false,"count":2,"input_count":3,"error_count":1,"partial":true,"executed":true,"elapsed_ms":612}

outline import reads entry events, creates documents, audits each one

A sink still emits meta and summary — the AOI envelope is universal across roles.
created events carry the new resource ID *and* the source_id from the upstream input, so the consumer can build a forward-mapping audit log.
A malformed input line produces an item-level error event but doesn't abort the run (--continue-on-error semantics from § 12.2 of the spec).
summary.partial:true with executed:true makes the outcome unambiguous: the work happened, and some inputs failed.

§ next

Build a tool that does this.

The conformance contract is small. Emit JSONL. Expose a schema. Terminate on a summary. Handle pipes cleanly. Redact secrets. The full checklist lives in the specification.

Read §18 · conformance