substack.search

stable Advanced

Search posts within a Substack publication.

GET /v1/substack/search

What you get#

A list of Substack results in Onekey's unified shape, in data (an array). An empty array is a normal, successful answer and is charged like any other; a source that reports "nothing found" as an error returns a free 404 not_found instead.

What it costs#

Advanced · 5 credits for a fresh fetch, charged only when it succeeds.
Free when served from cache (0.2 credit for a cached response over 100 KB).
Free if the request is invalid (never charged) or the source fails or reports not found (refunded).

Parameters#

Name	Type	Required	Default	What it is	Constraints
`pub`	string	yes	(required)	Allowlisted Substack publication host, e.g. www.astralcodexten.com	max 253 chars; must match `[a-z0-9.-]{3,253}`; trimmed, lowercased
`q`	string	yes	(required)	Search text	max 100 chars; must match `[^\x00-\x1f]{1,100}`; trimmed, repeated spaces collapsed

Request#

curl "https://api.onekey.dev/v1/substack/search?pub=www.astralcodexten.com&q=ai" \
  -H "x-api-key: YOUR_API_KEY"

Try it

Add your key to run this call right here. No key? Get one free. The key stays in this tab.

Recorded response#

A real Substack response, recorded and returned in Onekey's shape. Fields the platform does not provide are null.

json

{
  "success": true,
  "data": [
    {
      "content": {
        "id": "138968567",
        "title": "God Help Us, Let's Try To Understand AI Monosemanticity",
        "text": "Inside every AI is a bigger AI, trying to get out",
        "url": "https://www.astralcodexten.com/p/god-help-us-lets-try-to-understand",
        "createdAt": "2023-11-27T21:00:12Z"
      },
      "media": {
        "thumbnailUrl": "https://substack-post-media.s3.amazonaws.com/public/images/e3a2a957-0d98-4d59-8d41-b461c421c9d7_210x136.png"
      },
      "engagement": {
        "likes": 317,
        "comments": 227
      },
      "author": {
        "id": "12009663",
        "displayName": "Scott Alexander",
        "username": "astralcodexten",
        "avatarUrl": "https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fbucketeer-e05bbc84-baa3-437e-9518-adb32be77984.s3.amazonaws.com%2Fpublic%2Fimages%2F7b500d22-1176-42ad-afaa-5d72bc36a809_44x44.png"
      },
      "ext": {
        "audience": "everyone",
        "wordCount": 2991
      },
      "entity": {
        "slug": "god-help-us-lets-try-to-understand"
      }
    },
    {
      "content": {
        "id": "165939000",
        "title": "Make A Personalized AI Kids' Book",
        "text": "\"AI will probably lead to the end of the world, but in the meantime there will be great [presents]\"",
        "url": "https://www.astralcodexten.com/p/make-a-personalized-ai-kids-book",
        "createdAt": "2025-06-20T05:56:08Z"
      },
      "media": {
        "thumbnailUrl": "https://substackcdn.com/image/fetch/$s_!qYcr!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F588ed56b-6bf5-4fb7-9636-2c5aacbe0bdb_2548x2372.png"
      },
      "engagement": {
        "likes": 85,
        "comments": 16
      },
      "author": {
        "id": "12009663",
        "displayName": "Scott Alexander",
        "username": "astralcodexten",
        "avatarUrl": "https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fbucketeer-e05bbc84-baa3-437e-9518-adb32be77984.s3.amazonaws.com%2Fpublic%2Fimages%2F7b500d22-1176-42ad-afaa-5d72bc36a809_44x44.png"
      },
      "ext": {
        "audience": "only_paid",
        "wordCount": 941
      },
      "entity": {
        "slug": "make-a-personalized-ai-kids-book"
      }
    }
  ],
  "metadata": {
    "platform": "substack",
    "endpoint": "search",
    "cached": false,
    "stale": false,
    "age_s": 0,
    "fetched_at": "2026-01-01T12:00:00+00:00",
    "credits_charged": 5,
    "request_id": "7f3a9c2e5b1d4c8fa2e6d0b9c4f18e37"
  },
  "error": null
}

Field mapping#

How this endpoint's source fields become Onekey's unified schema. Fields the source lacks come back as null.

Source path	Onekey field	Transform
`id`	`content.id`	`toString`
`title`	`content.title`	-
`subtitle`	`content.text`	-
`canonical_url`	`content.url`	`safeUrl`
`post_date`	`content.createdAt`	`toIsoDate`
`cover_image`	`media.thumbnailUrl`	`safeUrl`
`reaction_count`	`engagement.likes`	`toNumber`
`comment_count`	`engagement.comments`	`toNumber`
`publishedBylines.0.id`	`author.id`	`toString`
`publishedBylines.0.name`	`author.displayName`	-
`publishedBylines.0.handle`	`author.username`	-
`publishedBylines.0.photo_url`	`author.avatarUrl`	`safeUrl`
`audience`	`ext.audience`	-
`slug`	`entity.slug`	-
`wordcount`	`ext.wordCount`	`toNumber`

Caching and freshness#

Fresh for about 2 minutes. Repeat calls in that window are served from cache and are free.
Between 2 minutes and 15 minutes the cached copy is still served instantly and marked stale: true while Onekey refreshes it in the background.
If the source is down when a refresh is needed, the last copy can be served for up to 1 hour more (marked stale).
A "not found" is remembered for 1 minute and is free.
The cache is shared across all customers, which is what keeps repeat calls cheap.

What can go wrong#

Status	Code	What to do
401	`unauthorized`	Check the `x-api-key` header.
402	`insufficient_credits`	Add credits; your balance must cover the price.
404	`not_found`	Unknown endpoint path.
422	`invalid_params`	Fix the parameters using the table above. Free.
429	`rate_limited`	Wait `Retry-After` seconds, then retry.
502	`upstream_error`	The source failed. Refunded; retry with backoff.

See Errors for the full list and retry guidance.

Status: stable (verified against the live source).