Docs / Concepts

Evidence

Evidence is the ordered protocol record that makes accepted, denied, failed, and replayed invocations inspectable.

Plain English

Evidence is the structured record of what happened at the capability boundary.

Why it exists

Logs are not enough when independent agents, hosts, applications, and infrastructure providers need to reconstruct outcomes.

Formal definition

Evidence is ordered invocation metadata emitted by a host and queryable by correlation ID for audit, debugging, verification, and export.

Concrete example

Ground the concept before the schema.

A denied schedule_technician invocation emits execution_denied with capability ID, version, host, sequence, and correlation ID.

schedule_technicianInvokable

Finds an available qualified technician and reserves a service window.

host: ServiceOpsHostpolicy: approval_requiredv1.0.0

Invocation trace

  1. 01 Actor

    Planning Agent

  2. 02 Capability

    schedule_technician

  3. 03 Host

    ServiceOpsHost

  4. 04 Policy

    manager_approval

  5. 05 Context

    job_context

  6. 06 Result

    Confirmed Appointment

evidence-event.json
json
{  "event_id": "evt_8f3a1c",  "event_type": "execution_denied",  "invocation_id": "inv_session_abc_001",  "capability_id": "schedule_technician",  "capability_version": "1.0.0",  "host_id": "service-ops-host",  "correlation": { "correlation_id": "session-abc" },  "sequence": 2,  "timestamp": "2026-06-16T15:14:22.104Z",  "outcome": "denied",  "payload": { "policy": "manager_approval" },  "redacted": true,  "assurance": { "level": "S1" }}

Relationships

Where this sits in the protocol.

Each concept should explain its neighbors so implementation teams can preserve the boundary across manifests, invocation, evidence, and tests.

Evidence is emitted after validation, denial, failure, or execution.

Replay uses evidence to reconstruct the ordered protocol trail.

Conformance tests should prove evidence shape and ordering.

Visual model

  1. 01Invocation starts with a correlation ID.
  2. 02Host emits typed evidence events in order.
  3. 03Replay returns the evidence stream for inspection.

Implementation notes

  • Use stable event types for started, completed, failed, denied, and replayed outcomes.
  • Redact sensitive payload fields while preserving decision metadata.
  • Make evidence queryable without requiring private host logs.

Common mistakes

  • Calling arbitrary logs evidence.
  • Recording only successful executions.
  • Dropping sequence and correlation fields.

Related concepts

Keep reading through the boundary.

Host →Invocation →Policy →