---
title: "Score text on five classic readability metrics"
method: POST
path: "/v1/text/readability"
tags: ["text"]
---

# Score text on five classic readability metrics

`POST /v1/text/readability`

## Request

- Base URL: `https://api.snipget.ai` (the document declares no server; this is the origin it was published from)
- URL: `https://api.snipget.ai/v1/text/readability`
- Auth: none declared

Returns Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog Index, SMOG, and Dale-Chall raw score, plus the raw counts (sentences, words, syllables, complex words, difficult words) so the caller can judge whether short-input metrics — notably SMOG, designed for 30-sentence samples — are meaningful. Pure algorithmic; no model calls. English-calibrated.

## Query parameters

- `include_receipt` boolean

## Headers

- `authorization` string, nullable
- `X-API-Key` string, nullable

## Request body

- TextReadabilityRequest
  - `text` string, required: Text body to score.
  - `include_grade_label` boolean: When True, include a recommended_audience label derived from Flesch RE.
  - `include_trace` boolean

## Response `200`

Successful Response

- TextReadabilityResponse: Success envelope for `/v1/text/readability` — `result` carries this utility's precise shape.
  - `status` string
  - `confidence` number, required
  - `result` object, required: Result of :func:`score`.
    - `input` string, required
    - `is_valid` boolean, required
    - `why_invalid` string
    - `sentence_count` integer
    - `word_count` integer
    - `syllable_count` integer
    - `complex_word_count` integer
    - `difficult_word_count` integer
    - `flesch_reading_ease` number
    - `flesch_kincaid_grade` number
    - `gunning_fog` number
    - `smog` number
    - `dale_chall` number
    - `recommended_audience` string
  - `meta` ResponseMeta: Metadata attached to every successful response.
    - `version` string
    - `build` string
    - `elapsed_ms` integer
    - `cost_units` integer: Cost units charged for this call: one per item processed (a batch of N items = N; live-registry lookups bill 2 per item). A call is one request; cost units are the billing measure.
    - `request_id` string, nullable
    - `trace` string[], nullable
    - `rate_limit_remaining` integer, nullable
    - `rate_limit_reset` integer, nullable
    - `quota_remaining` integer, nullable: Cost units left in the plan's monthly included bucket before this call's charge lands (None on unlimited tiers).
    - `quota_reset` integer, nullable: Unix timestamp when the monthly included bucket resets.
    - `credit_remaining_usd` number, nullable: Prepaid overage-allowance balance in USD, populated once the included cost units are used up and this call is drawing on it.
    - `receipt` ReceiptMeta: Opt-in execution receipt (ADR #68 B1) — caller-verifiable hashes. Requested with the ``include_receipt=true`` query parameter (free, like ``include_trace``). Reproduce either hash with any RFC 8785 (JCS) library: ``input_hash = sha256(jcs({"tool": <request path>, "args": <your JSON body minus include_trace/include_receipt>}))``; ``result_hash = sha256(jcs(result))``. For deterministic tools (everything except the generators) the same input on the same ``build`` reproduces ``result_hash`` — disputes are honored by replay.
      - `receipt_id` string, required
      - `build` string, required
      - `input_hash` string, nullable
      - `result_hash` string, nullable
      - `error` string, nullable
      - `message` string, nullable

## Other responses

- `400`: Input was syntactically valid but semantically unusable (`INVALID_INPUT`). Not retryable without changing the input.
- `401`: Missing or unrecognized API key. Send it as `Authorization: Bearer <key>` or `X-API-Key: <key>`. Keys are issued at https://snipget.ai.
- `403`: The key is valid but this caller may not use it: the request IP is outside the key's allowlist (`IP_NOT_ALLOWED`) or the account is deactivated (`ACCOUNT_DEACTIVATED`).
- `422`: The request body failed schema validation (`INVALID_REQUEST`). `details` lists the per-field errors. Not retryable without changing the request.
- `429`: Two distinct conditions share this status — branch on `error_code`. **`RATE_LIMITED`** is a per-second throughput throttle: retry after `retry_after_seconds` (the precise float; the `Retry-After` header is the same value rounded up). **`QUOTA_EXCEEDED`** is monthly capacity and is NOT retryable: recovery depends on `limit_type` — upgrade (`monthly_quota`), buy an overage allowance (`included_exhausted`), or top up (`overage_balance_exhausted`).
- `503`: A transient, retryable service condition — branch on `error_code`. **`MAINTENANCE_MODE`**: an admin-toggled maintenance window (auth, portal, and webhook surfaces stay up). **`UPSTREAM_UNAVAILABLE`**: a utility's external data source (PubChem, RxNorm, ClinicalTrials.gov, the FX feed, NPPES…) is down, blocking us, or timed out. **`UPSTREAM_RATE_LIMITED`**: that external source is throttling Snipget (it returned a 429) — the caller's own rate is fine, so this is NOT our `RATE_LIMITED` (429); it's a service-side throttle. All three are retryable; wait for `retry_after_seconds` / the `Retry-After` header when present.

---

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