capsule-emit

Know what your AI agent did — and let anyone verify it.

One emit() call at each consequential action builds an anchored, verifiable ledger of what your agent did — each entry sealed (content-addressed by hash) and checkable by anyone, without trusting you.

from capsule_emit import emit

result = {"po_id": "PO-7781"}            # whatever your action returned

cap = emit(
    action="write_order",
    operator="acme-co",                  # the accountable tenant
    developer="po-agent@v1",             # the agent identity + version
    agent_input={"vendor": "Frobozz Supply", "total": 1240.19},
    agent_output=result,
    model={"provider": "anthropic", "model_id": "claude-sonnet-4-6"},
    verdict="executed",                  # executed | confirmed | denied | blocked
    effect={"type": "write_order", "status": "dispatched"},
)
print(cap.capsule_id, cap.anchored)      # sealed; anchor submitted async (offline? emit(..., anchor=False))

pip install capsule-emit

capsule-emit is the producer layer for the Agent Action Capsule — a SCITT statement profile. You add one line at the moment your agent does something consequential; you get back a digest-committed, content-addressed capsule — anchored to a public log — that a third party who trusts neither you nor your agent can independently verify.

Why you need this

Agents now move money, change records, and act across organizational boundaries. When something goes wrong — or someone asks "did your agent really do that, and was it authorized?" — what's your proof?

Your logs are your own word. They're mutable, they live in your database, and they mean nothing to an auditor, a counterparty, or a regulator who has no reason to trust your systems. There's no way for an outside party to confirm a log wasn't edited after the fact.

A capsule is different: its content is committed to a hash the moment the action happens, and that hash is recorded in a public append-only log.* Anyone can verify it offline, from the bytes alone — without trusting you.

* "Public log" ≠ public data. Only a one-way fingerprint (a SHA-256 digest) and a timestamp are logged — your prompts, payloads, vendors, and amounts never leave your machine. What's on the log, and what isn't →

Why your existing stack can't do this

These layers answer different questions — a capsule fills the gap of what an agent provably did:

Layer	Examples	Answers	Doesn't answer
Identity	DIDs, SPIFFE, Agent Cards	Who is the agent?	What it did
Authorization	OPA, policy, permits	What is it may to do?	What it actually did, or the outcome
Observability	Datadog, audit logs, your DB	What you say happened	Nothing to a party who doesn't trust you — mutable, self-attested
Agent Action Capsule	capsule-emit	What it did, provably	(composes with layers above)

A capsule records the action and its outcome, with a confirmed-effect binding so a dispatched attempt can't be passed off as a completed effect (the may/did distinction: approved ≠ executed ≠ confirmed). It records on every verdict, including refusals — a blocked capsule is auditor-grade evidence that a gate worked.

Where you start, and where it goes

Start here. Call emit() at each consequential action. You get an anchored, verifiable ledger of what your agent did — each capsule appended locally to ledger.jsonl, its digest written to a public log. That's the whole starting point. Everything below is optional depth you grow into — no rewrite.

Then climb, one rung at a time:

• Capture more, write less — a decorator adapter (MCP / LangChain / CrewAI / Hermes / Goose / ADK) seals each wrapped tool call automatically; the agentgateway adapter seals all consequential traffic at the gateway chokepoint — no per-tool changes needed.
• Link records into trails — chain a confirmation capsule to its parent: approved → executed → confirmed, human-in-the-loop, and disclosure all ride this. This is where may/did becomes a verifiable sequence — and a different agent can chain to yours by id alone. → emit(..., confirms=parent_id) · within & across agents
• Declare now, enforce later — a manifest.md declares your rules; a compatible gateway enforces the same file, with no change to your emit() calls.

The unit is the capsule (one action). What you keep and grow is the ledger (the anchored trail). Chaining links specific capsules within it. Start with the ledger; add the rest when you need it. → walk it end-to-end in the tutorials.

What you get back

emit() returns an EmitResult — cap.capsule_id, cap.anchored, and cap.capsule (the capsule itself, plain JSON you can store or hand to anyone). It carries the capsule_id (a SHA-256 content address), the accountable operator + developer, the may/did verdict, the effect (and its dispatched-vs-confirmed status), and digests of your input and output — your inputs and outputs are committed by hash; you hold the raw values, the capsule does not (only their digests).

→ Field-by-field, the two-tier structure, and how each layer is captured: docs/anatomy.md.

Anchoring — where the proof lives

Anchor is on by default. On emit(), the capsule's digest only is submitted — async, non-blocking — to an RFC 9162 SCITT transparency log, so this exact capsule's existence is recorded at that time and independently checkable against the log. (cap.anchored reports the submission; surfacing the log's inclusion receipt back onto the result is on the near-term roadmap — today the digest is on the log and checkable there.)

• What's logged: a SHA-256 digest — nothing else. Your payloads never leave your machine.
• Where: the free hosted log at https://anchor.agentactioncapsule.org/v1/digest (no signup, no key).
• Self-host or repoint: the log service (capsule-anchor) is open-source — AAC_ANCHOR_URL=… or emit(..., anchor_url=…).
• Offline: emit(..., anchor=False) seals locally, skips the network.

Why bother: a self-hosted log you control isn't proof to an outsider; a shared, append-only transparency log is. That's what makes the capsule checkable by someone who trusts neither party.

Verify

The verifier ships in the spec package — check any capsule (or a whole ledger) from the bytes alone, no keys/network/clock:

pip install agent-action-capsule
agent-action-capsule verify --store ./ledger.jsonl

Tamper with one byte and verification fails. The verifier is independent of capsule-emit on purpose — any tool can produce a capsule; any party can verify one. (Every emit() also appends to a local JSONL ledger — view it with capsule-emit ledger view ./ledger.jsonl.)

Framework adapters

One emit() per tool call, regardless of framework — thin adapters over one shared base:

from capsule_emit.adapters.mcp import MCPCapsuleEmitter
emitter = MCPCapsuleEmitter(operator="acme-co", developer="my-agent@v1")

@emitter.tool("write_order")
def write_order(vendor: str, total: float) -> dict: ...

Adapter	What it wraps
MCP	Model Context Protocol tool endpoints — any Python callable, decorator-based
Google ADK	Google Agent Development Kit tool calls, one capsule per completed tool invocation
agentgateway	Rust proxy for MCP/A2A/LLM traffic; seals all tools/call at the gateway chokepoint
LangChain	LangChain callback handler; fires on on_tool_start/on_tool_end automatically
CrewAI	Wraps a CrewAI tool object; emits one capsule per call, input and output captured
Goose	Block's open-source AI agent; Goose tools are MCP tools, so the MCP adapter applies
Hermes	Custom agent loops; call after_tool(...) explicitly after any tool finishes
Dapr	Dapr actor and service invocation; wraps Dapr tool calls as capsule-emitting steps

Each adapter page has a paste-ready prompt for a coding agent to wire emission into your tools: docs/adapters/.

Declare now, enforce later — same file

A flows/<action>/manifest.md declares autonomy + constraints; capsule-emit reads it to declare (no enforcement). A compatible gateway reads the same file and enforces — with no change to your emit() calls. → docs/going-deeper.md.

Documentation

New here? Written to be read top-to-bottom, no standards background needed:

• Tutorials — five-minute, copy-paste sessions: your first capsule → confirming & chaining → reading your ledger → declaring rules.
• Concepts in plain words — the seven words (capsule, seal, may/did, chain, break, anchor, ledger), each tied to a field or command.
• Anatomy of a capsule — exactly what gets sealed, the two-tier structure, how each layer is captured.
• Chaining — within one agent, and across agents — capsules link by content address into verifiable trails, including cross-organizational chains; why the ledger is a DAG, not one line.
• Why anchoring makes it trustworthy — why a record you keep isn't proof to anyone else, and how a shared append-only log fixes it. The heart of it.
• The public log, explained — plain-English + FAQ: the transparency log, how Merkle proofs work, what's visible vs hidden, what you can progressively share. For when someone asks "you're putting our data on a public log?"
• Adapters — decorator adapters (MCP / LangChain / CrewAI / Hermes / Goose / ADK) seal each wrapped tool call; agentgateway seals all tools/call traffic at the gateway layer. Paste-to-your-coding-agent prompt on each page.
• Going deeper — and popping out — down into the spec + scitt-cose substrate to verify it yourself; up to a compatible enforcement gateway when you want capsules to block, not just record.

How it fits

capsule-emit  →  agent-action-capsule (spec + reference verifier)
                        ↓
                 scitt-cose (COSE_Sign1 + SCITT receipt verification)

capsule-emit produces; agent-action-capsule is the specification + verifier; scitt-cose verifies the transparency-log substrate. Separate on purpose.

Status

Alpha — API stable, not yet 1.0. The underlying specification is an individual IETF Internet-Draft, not an RFC; no RFC number is claimed.

Conformance & spec tracking. Every capsule stamps its spec_version + format_version, and capsule-emit produces capsules conforming to the current draft (draft-mih-scitt-agent-action-capsule, format 2) — proven by the independent agent-action-capsule verifier and its frozen conformance vectors, not by self-assertion. When the spec revises, the version bumps and older capsules keep verifying; that's how this implementation stays tracked to the standard.

Provenance, neutrality & governance

Developed by Action State Group, Inc. and published as open-source software (Apache-2.0), with a clean transfer path to a neutral home (foundation donation or community project) as the ecosystem matures. The content is product-free — the emission layer, adapters, ledger utilities, and a manifest parser; nothing tenant- or product-specific. No primacy is claimed; the value is an interoperable, independently-verifiable record format. Discussion venue: the IETF SCITT Working Group (scitt@ietf.org).

License

Apache-2.0 — see LICENSE.

Patent posture: All six provisional patent applications related to this specification were expressly abandoned on July 6, 2026. No license is required. See agentactioncapsule.org/ip for details.