LanguageTool

LanguageTool is an open-source proofreading and grammar checking tool that supports more than 25 languages. The HTTP API enables developers to programmatically check texts for grammar and style issues, list supported languages, and manage personal dictionaries.

LanguageTool publishes 3 APIs on the APIs.io network: Check API, Languages API, and Words API. Tagged areas include Grammar, Language, Proofreading, Spell Check, and Style Check.

The LanguageTool catalog on APIs.io includes 1 Spectral governance ruleset.

LanguageTool’s developer surface includes documentation, GitHub presence, and 7 more developer resources.

🌐 Visit website 📡 Source on GitHub

31.7/100 thin ▬ flat Agent 20/100 agent aware saas Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

AccessFreemium

1 APIs

Grammar Language Proofreading Spell CheckStyle CheckText Analysis

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 31.7/100 · thin

Contract Quality 12.0 / 23

Developer Ergonomics 1.7 / 18

Access Clarity 6.6 / 18

Operational Transparency 1.5 / 12

Contract Governance 1.1 / 11

Discoverability 6.2 / 9

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 20/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/languagetool: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 3

Individual APIs this provider publishes, each with its own machine-readable definition.

LanguageTool Check API

The Check API from LanguageTool — 1 operation(s) for check.

LanguageTool Languages API

The Languages API from LanguageTool — 1 operation(s) for languages.

LanguageTool Words API

The Words API from LanguageTool — 3 operation(s) for words.

Open Collections 5

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

API Collection

OPEN COLLECTION

LanguageTool HTTP Check API

OPEN COLLECTION

LanguageTool HTTP Check Languages API

OPEN COLLECTION

LanguageTool HTTP Check Words API

OPEN COLLECTION

LanguageTool HTTP API

OPEN COLLECTION

Pricing Plans 1

Published pricing tiers and plan structures.

Languagetool Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Languagetool Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Languagetool Finops

FINOPS

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

LanguageTool API Rules

5 rules · 3 warnings 2 info

SPECTRAL

JSON Schema 1

Standalone JSON Schema definitions for this provider's data models.

LanguageTool Match

8 properties

JSON SCHEMA

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Languagetool Domain Security

TLSv1.3 · DMARC

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Languagetool Agentic Access

5 operations · 3 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

Build 1

SDKs, sample code, and the tooling you integrate with

GitHub

GitHub

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Commercial 2

Pricing, plans, and the legal terms of use

PrivacyPolicy

PrivacyPolicy

TermsOfService

TermsOfService

Company 2

The organization behind the API

LinkedIn

Website

Website

Other 1

Properties that don't map to a standard resource type

Developer

Developer

Source (apis.yml)

aid: languagetool
name: LanguageTool
description: LanguageTool is an open-source proofreading and grammar checking tool that supports more than 25 languages. The
  HTTP API enables developers to programmatically check texts for grammar and style issues, list supported languages, and
  manage personal dictionaries.
type: Index
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: medium
  source:
  - plans
  generated: '2026-07-22'
  method: derived
position: Consuming
access: 3rd-Party
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/languagetool.png
tags:
- Grammar
- Language
- Proofreading
- Spell Check
- Style Check
- Text Analysis
created: '2025-02-08'
modified: '2026-05-19'
url: https://raw.githubusercontent.com/api-evangelist/languagetool/refs/heads/main/apis.yml
specificationVersion: '0.23'
apis:
- aid: languagetool:languagetool-check-api
  name: LanguageTool Check API
  description: The Check API from LanguageTool — 1 operation(s) for check.
  humanURL: https://languagetool.org/http-api/
  baseURL: https://api.languagetool.org/v2
  tags:
  - Check
  properties:
  - type: OpenAPI
    url: openapi/languagetool-check-api-openapi.yml
  - type: Documentation
    url: https://languagetool.org/http-api/
  - type: SwaggerUI
    url: https://languagetool.org/http-api/swagger-ui/
  - type: JSONSchema
    url: json-schema/languagetool-match-schema.json
- aid: languagetool:languagetool-languages-api
  name: LanguageTool Languages API
  description: The Languages API from LanguageTool — 1 operation(s) for languages.
  humanURL: https://languagetool.org/http-api/
  baseURL: https://api.languagetool.org/v2
  tags:
  - Language
  tags_raw:
  - Languages
  properties:
  - type: OpenAPI
    url: openapi/languagetool-languages-api-openapi.yml
  - type: Documentation
    url: https://languagetool.org/http-api/
  - type: SwaggerUI
    url: https://languagetool.org/http-api/swagger-ui/
  - type: JSONSchema
    url: json-schema/languagetool-match-schema.json
- aid: languagetool:languagetool-words-api
  name: LanguageTool Words API
  description: The Words API from LanguageTool — 3 operation(s) for words.
  humanURL: https://languagetool.org/http-api/
  baseURL: https://api.languagetool.org/v2
  tags:
  - Word
  tags_raw:
  - Words
  properties:
  - type: OpenAPI
    url: openapi/languagetool-words-api-openapi.yml
  - type: Documentation
    url: https://languagetool.org/http-api/
  - type: SwaggerUI
    url: https://languagetool.org/http-api/swagger-ui/
  - type: JSONSchema
    url: json-schema/languagetool-match-schema.json
common:
- type: AgenticAccess
  url: agentic-access/languagetool-agentic-access.yml
- type: DomainSecurity
  url: security/languagetool-domain-security.yml
- type: LinkedIn
  url: https://www.linkedin.com/company/languagetool
- type: Website
  url: https://languagetool.org
- type: Documentation
  url: https://languagetool.org/http-api/
- type: Developer
  url: https://dev.languagetool.org/
- type: GitHub
  url: https://github.com/languagetool-org/languagetool
- type: PrivacyPolicy
  url: https://languagetool.org/legal/privacy
- type: TermsOfService
  url: https://languagetool.org/legal/terms
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

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