Failure Sequence Forge

Create an unguessable temporary GET endpoint for testing retry and recovery behavior. Each request atomically consumes exactly one allowlisted failure or terminal-success step. Responses use a fixed JSON body and fixed safe headers; callers cannot provide bodies, headers, redirects, or destinations.

Use when

A retry loop, SDK, or circuit breaker must recover across an ordered sequence of HTTP failures.
A short-lived endpoint should advance atomically from retryable failures to one terminal success.

Do not use when

The test requires arbitrary response bodies, headers, redirects, or a production endpoint.
More than eight attempts or more than 30 minutes of retention is required.

Invocation contract

HTTP: /v1/tools/failure-sequence-forge
Version: 0.1.0
Mode: ephemeral
Idempotency: required
Retention: The sequence record and atomic hit counter remain in Valkey for at most 30 minutes. The URL token has 256 bits of entropy and is never listed.
Tested with: HTTP/1.1, HTTP/2, parallel GET consumers, MCP Streamable HTTP

Positive and negative examples

{
  "input": {
    "steps": [
      {
        "status": 429,
        "delay_ms": 0
      },
      {
        "status": 500,
        "delay_ms": 0
      },
      {
        "status": 200,
        "delay_ms": 0
      }
    ],
    "ttl_seconds": 300
  },
  "output": {
    "fixture_url": "https://lab.example/v1/fixtures/failure-sequence/fsf_example",
    "sequence": [
      429,
      500,
      200
    ],
    "expires_at": "2026-07-24T12:05:00.000Z",
    "max_hits": 3,
    "capability_entropy_bits": 256,
    "behavior": {
      "fixed_body_format": "json",
      "retry_after_seconds_for_429": 1,
      "max_delay_ms_per_step": 2000,
      "exhausted_status": 410
    }
  },
  "negative": [
    {
      "scenario": "The test requires arbitrary response bodies, headers, redirects, or a production endpoint.",
      "expected_error": "NOT_COVERED",
      "charged": false
    }
  ]
}

Deterministic errors

Code	Retry	Charged	Recovery
INVALID_INPUT	false	false	Correct the request to match input_schema.
NOT_COVERED	false	false	Check dataset scope or submit a capability request.
TOOL_PAUSED	true	false	Wait for the operator to resume the tool.
RATE_LIMITED	true	false	Retry after the response Retry-After interval.
DEPENDENCY_UNAVAILABLE	true	false	Retry with the same idempotency identity.

Full machine manifest

The HTTP, OpenAPI, MCP, llms.txt, and ARD descriptions are generated from this same registry record.

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