generated: '2026-09-05'
method: probed
source: https://zbiotics.com/llms.txt, https://zbiotics.com/api/ucp/mcp
docs: https://zbiotics.com/llms.txt
summary: >-
  A rate limit is asserted in prose and could not be characterised in practice. ZBiotics' llms.txt
  tells agents the MCP endpoint is rate-limited per IP and to back off on 429, but publishes no
  number, no window and no burst, and the endpoint returns no rate-limit headers. An agent gets
  one runtime signal - a 429, after the fact.
limit_count: 0
limits:
- scope: per-ip
  surface: https://zbiotics.com/api/ucp/mcp
  window: null
  limit: null
  burst: null
  status_on_exhaustion: 429
  documented: true
  quantified: false
  source: https://zbiotics.com/llms.txt
  quote: 'Respect rate limits. The MCP endpoint is rate-limited per IP. Back off on 429 responses.'
response_headers:
  ratelimit_standard: []
  x_ratelimit: []
  retry_after: false
  observed: []
  detail: >-
    No RateLimit-Limit / RateLimit-Remaining / RateLimit-Reset (RFC 9239-style), no X-RateLimit-*,
    and no Retry-After appeared on any response. Six consecutive tools/list POSTs all returned 200
    and none carried a limit header, so no limit was reached and none is advertised in advance.
cost_signal:
  header: shopify-complexity-score
  also: shopify-complexity-score-v2
  observed:
  - request: 'POST /api/ucp/mcp tools/list'
    value: 34
  - request: 'GET /'
    value: 274
  detail: >-
    A per-request cost meter is returned, but no budget, bucket size or refill rate is published
    against it, so an agent cannot compute headroom from it. Recorded as a cost signal, not as a
    rate limit.
gaps:
- No numeric limit, window or burst is published anywhere on a ZBiotics host.
- No pre-emptive header, so an agent cannot slow down before being refused.
- >-
  limit_count is 0 deliberately: a stated existence of a limit is not a limit an agent can plan
  against, and recording a fabricated number to fill the field would be worse than the gap.
x-evidence:
  fetched: '2026-09-05'
  probes:
  - url: https://zbiotics.com/api/ucp/mcp
    method: POST
    repetitions: 6
    http_statuses: [200, 200, 200, 200, 200, 200]
    rate_limit_headers_seen: none
  - url: https://zbiotics.com/llms.txt
    http_status: 200