specification: API Commons Rate Limits
specificationVersion: '0.1'
schema: https://raw.githubusercontent.com/api-evangelist/interface-research/main/schema/api-commons.yml#/$defs/RateLimits
provider: University of Tokyo
providerId: university-of-tokyo
created: '2026-06-03'
modified: '2026-08-19'
reconciled: false
tags:
- Education
- Higher Education
- University
- Rate Limiting
description: >-
  The University of Tokyo publishes no rate limit for any of its interfaces, and no 429 was
  observed on any probe. What it does enforce instead is edge access control, and it is
  unusual enough to be the operative constraint: repository.dl.itc.u-tokyo.ac.jp returns
  HTTP 406 to a desktop-browser User-Agent and 200 to a plain client (inverted from the usual
  bot challenge), while da.dl.itc.u-tokyo.ac.jp returns HTTP 403 on /portal/search to every
  external automated client regardless of User-Agent. Paging limits are protocol-level:
  the Archives Portal caps OAI-PMH ListRecords at 100 records per resumptionToken page, and
  its documented search API caps items_per_page at 200.
notes: >-
  Re-verified 2026-08-19. No Retry-After, X-RateLimit-* or quota header was returned by any
  endpoint. Harvest at low rate and identify yourself with a real contact string; the
  repository's robots.txt disallows /api/, /oai and /search.
sources:
- https://raw.githubusercontent.com/api-evangelist/university-of-tokyo/refs/heads/main/apis.yml
- https://da.dl.itc.u-tokyo.ac.jp/portal/help/api
- https://repository.dl.itc.u-tokyo.ac.jp/robots.txt
- https://repository.dl.itc.u-tokyo.ac.jp/api/records/
method: probed
generated: '2026-08-19'
responseCodes:
  throttled: null
  throttled_note: >-
    No 429 was observed on any endpoint. The status codes that actually gate access are 406
    (repository, browser User-Agent) and 403 (Archives Portal search, all automated clients).
limits:
- name: OAI-PMH ListRecords page size
  scope: protocol
  metric: records-per-page
  limit: 100
  source: https://da.dl.itc.u-tokyo.ac.jp/portal/help/api
  notes: Archives Portal cap, documented by the university. Continue with resumptionToken.
- name: Archives Portal search page size
  scope: protocol
  metric: items-per-page
  limit: 200
  source: https://da.dl.itc.u-tokyo.ac.jp/portal/help/api
  notes: >-
    Documented maximum and also the default when items_per_page is omitted. Endpoint returns
    403 to external automated clients, so this is documented rather than observed.
- name: Repository records default page size
  scope: client
  metric: records-per-page
  limit: 10
  notes: Observed default on /api/records/. Overridable with ?size=. No documented ceiling.
- name: Global request rate
  scope: client
  metric: requests-per-minute
  limit: none published
  notes: No published limit and no throttling observed.
policies:
- name: Backoff Strategy
  description: >-
    Exponential backoff with jitter and off-peak harvesting. No Retry-After is sent, so back
    off on any non-200 rather than waiting for a hint.
- name: User-Agent Policy
  description: >-
    Send a plain client User-Agent with a contact string to repository.dl.itc.u-tokyo.ac.jp;
    a browser-shaped User-Agent returns 406 there. Send a browser-shaped User-Agent to
    da.dl.itc.u-tokyo.ac.jp item paths. The two institution hosts require opposite settings.
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com