Protocol bindings¶

ASC complements existing protocols. It does not redefine their native status or error semantics.

HTTP¶

A synchronous request MAY project an ASC status to an appropriate HTTP status and include ASC in a Problem Details-style response:

HTTP/1.1 429 Too Many Requests
Content-Type: application/problem+json
Retry-After: 2

{
  "type": "urn:agent-status:RATE_LIMITED",
  "title": "Agent dependency rate-limited",
  "status": 429,
  "agent_status": {
    "code": 5001,
    "name": "RATE_LIMITED",
    "scope": "tool_call",
    "terminal": false
  },
  "retry": {
    "retryable": true,
    "safe": true,
    "after_ms": 2000
  }
}

For asynchronous work, HTTP reports the operation on the status resource, not the outcome of the represented agent run:

POST   /agent-runs             -> HTTP 202 + ASC-1000 ACCEPTED
GET    /agent-runs/123         -> HTTP 200 + current ASC envelope
POST   /agent-runs/123/approve -> HTTP 200 or 202
DELETE /agent-runs/123         -> HTTP 204 + ASC-3004 CANCELLED

If run 123 ends with INTERNAL_ERROR, a successful GET /agent-runs/123 still returns HTTP 200.

gRPC¶

A failed RPC SHOULD retain the closest canonical gRPC status and include ASC in typed status details or response metadata.

ASC	gRPC projection
`RATE_LIMITED`	`RESOURCE_EXHAUSTED`
`PERMISSION_DENIED`	`PERMISSION_DENIED`
`TIMEOUT`	`DEADLINE_EXCEEDED`
`DEPENDENCY_UNAVAILABLE`	`UNAVAILABLE`
`FAILED_PRECONDITION`	`FAILED_PRECONDITION`
`ABORTED_CONCURRENCY`	`ABORTED`
`INTERNAL_ERROR`	`INTERNAL`
`DATA_LOSS`	`DATA_LOSS`

Agent2Agent¶

A2A task state remains the coarse lifecycle signal. ASC refines it:

A2A state	Example ASC status
Submitted	`ACCEPTED`
Working	`RUNNING`, `RETRY_SCHEDULED`
Input required	`HUMAN_INPUT_REQUIRED`
Auth required	`AUTHENTICATION_REQUIRED`
Completed	`SUCCESS`, `SUCCESS_WITH_WARNINGS`, `PARTIAL_SUCCESS`
Rejected	`GUARDRAIL_BLOCKED`, `PERMISSION_DENIED`
Failed	A terminal `5xxx`, `6xxx`, or withholding `7xxx` status
Cancelled	`CANCELLED`

An implementation SHOULD carry ASC in a versioned A2A extension rather than replace A2A's lifecycle state.

Model Context Protocol¶

Unknown tools and malformed MCP requests remain JSON-RPC protocol errors. A tool execution failure remains a successful protocol response with isError: true and MAY include ASC as structured content:

{
  "content": [
    {
      "type": "text",
      "text": "The customer record is read-only for this principal."
    },
    {
      "type": "resource",
      "resource": {
        "mimeType": "application/agent-status+json",
        "text": "{\"code\":4002,\"name\":\"PERMISSION_DENIED\",\"scope\":\"tool_call\"}"
      }
    }
  ],
  "isError": true
}

OpenTelemetry¶

ASC augments OpenTelemetry span status. Recommended low-cardinality span attributes are:

agent.status.code             = 5001
agent.status.name             = "RATE_LIMITED"
agent.status.class            = "transient_failure"
agent.status.kind             = "status"
agent.status.scope            = "tool_call"
agent.status.terminal         = false
agent.status.retryable        = true
agent.status.retry_safe       = true
agent.lifecycle.phase         = "EXECUTING"

Non-terminal transitions and 8xxx occurrences SHOULD be span events. A transient child attempt that later succeeds SHOULD NOT force the parent task span to remain in an error state.

Metrics MUST use bounded dimensions. Prompts, user identifiers, run identifiers, URLs, and free-form messages MUST NOT be metric labels.

Process exit status¶

A command-line tool MAY provide a lossy exit-code projection for shell use, but it SHOULD write the full ASC envelope to standard output, standard error, or a declared file. Process exit status is not a substitute for the envelope.