Quickstart: seal your first capsule

From install to a witnessed, verified record in a few minutes — using seal(), the canonical one-call API.

1. Install

pip install capsule-emit

2. Seal an action

Call seal() once at each consequential action — the payload is the first positional argument, never a keyword. action, operator, developer, and agent_output are what you'll always pass; model, verdict, and effect are optional (adapters fill in what they can — the MCP adapter, for example, sees the tool boundary, not the LLM, so pass model explicitly there if you want it sealed).

from capsule_emit import seal

result = place("Frobozz Supply", "4210.00", "PO-0047")  # your tool logic

cap = seal(
    {"vendor": "Frobozz Supply", "total": "4210.00"},  # payload — first arg; monetary values are strings, not floats
    action="submit_order",
    operator="acme-co",                # accountable tenant
    developer="po-agent@v1",           # agent identity + version
    agent_output=result,
    model={"provider": "example-provider", "model_id": "example-model"},
    verdict="executed",               # a verdict_class: executed | blocked | denied | …
    effect={"type": "submit_order", "status": "dispatched"},
)
print(cap.capsule_id, cap.signature)   # sealed, signed, and witnessed by default

3. Where it's witnessed

By default, every seal() folds the capsule into your ledger's checkpoint/witness stream: roughly every 100 entries (or 15 minutes), a signed checkpoint of the whole ledger — never capsule content — is registered with the public witness, a SCITT Transparency Service, at witness.agentactioncapsule.org, no signup, no key. Set CAPSULE_WITNESS=off (or pass witness=False) to seal fully offline; set CAPSULE_WITNESS_URL or pass witness_url=… to point at your own Transparency Service. The older per-capsule anchor channel (cap.anchored, anchor=True / CAPSULE_ANCHOR=legacy-on) is a legacy, explicit opt-in kept only as a rollback path — it has not been the default egress path since 0.5.0. See the adoption ladder for the full rung-by-rung path.

4. Verify

Each seal() also appends the sealed capsule to a local ledger.jsonl by default — that’s the file you verify, offline:

# verify a ledger of sealed capsules, offline — no keys or network needed
capsule-emit verify --store ledger.jsonl

  VALID

1/1 VALID

Adapters: seal from your framework

You don’t have to call seal() by hand. Thin adapters seal one capsule per tool call across the framework you already use — MCP / any callable (a decorator), LangChain / LangGraph (a callback), CrewAI (a tool wrap), and Goose (companion MCP server or @emitter.tool() decorator, verified against Goose v1.39.0). A gateway integration (agentgateway) seals at the chokepoint every consequential action flows through — one policy point instead of N integrations (via the gateway's mcpGuardrails ExtMcp hook). Any custom loop works via one call at the tool boundary. Per-framework guides: docs/adapters/ — including the Goose extension and the agentgateway adapter.