LanguageTool API

Name: LanguageTool API
Brand: LanguageTool API
Availability: InStock

✓ Official Vendor SpecAI/MLLanguage Modelsnone5 EndpointsREST

For Agents

Check text for spelling, grammar, and style errors with LanguageTool and apply structured correction suggestions across many languages.

Install Jentic One Beta

Connect the LanguageTool API to your agent

Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the LanguageTool API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.

Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.

Step 1: Jentic One Host machine

# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh

Step 2: Agent machine

# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register       # connects your agent to your Jentic One instance

Jentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.

Capabilities

What an agent can do with LanguageTool API.

Check a block of text for spelling, grammar, and style issues with structured suggestions

Retrieve the list of languages and language variants LanguageTool supports

Add words to a user's personal dictionary so they are ignored on future checks

GET STARTED

Start building with LanguageTool API

Explore with Jentic

View OpenAPI Document

Use Cases

Patterns agents use LanguageTool API for, with concrete tasks.

★ Editorial Proofreading Pipeline

A content team runs draft articles through the LanguageTool /check endpoint before publishing, surfacing spelling, grammar, and style issues with suggested replacements. Each issue includes the offending offset, rule ID, and one or more replacement strings so the editor can accept or reject suggestions in bulk. This catches mistakes that human review misses on long-form content.

Send the article body to /check with language='en-GB', collect all matches with their offsets and replacements, and apply only the high-confidence suggestions automatically.

Multi-Language Form Validation

A web product accepts user-generated text in multiple languages and uses LanguageTool to check each submission against the language declared by the user. The /languages endpoint provides the supported language and variant list to populate the language picker. This keeps user content readable without forcing a single working language.

Fetch /languages to populate a language selector, then call /check with the user's chosen language code on every submission and surface the top three suggestions per match.

Personalised Dictionary for Brand Terms

A team adds product names, internal jargon, and author surnames to a LanguageTool personal dictionary so they stop being flagged as misspellings. The /words/add and /words/delete endpoints maintain that list per user, and /words returns the current entries. This avoids noisy false positives in brand-heavy content.

POST 'Jentic' and 'MAXsystem' to /words/add for the current user, then re-run /check on the draft to confirm those terms are no longer flagged.

AI Agent Writing Assistant

An AI agent embedded in a writing tool uses LanguageTool through Jentic to grade and rewrite drafts. The agent searches Jentic for grammar checking, loads the /check schema, and submits the text without wiring LanguageTool client setup. Suggestions are then merged into the agent's revision step.

Use Jentic to call LanguageTool /check on the user's draft, then rewrite the text by applying the highest-confidence suggestion for each match before returning the cleaned version.

Key Endpoints

5 endpoints — the languagetool api checks text for spelling, grammar, and style issues across 30+ languages and returns structured suggestions with replacements, rule ids, and offsets.

METHOD

PATH

DESCRIPTION

POST

/check

Check text for grammar, spelling, and style issues.

GET

/languages

List supported languages and variants.

GET

/words

List words in the user's personal dictionary.

POST

/words/add

Add a word to the user's personal dictionary.

POST

/words/delete

Remove a word from the user's personal dictionary.

POST

/check

Check text for grammar, spelling, and style issues.

GET

/languages

List supported languages and variants.

GET

/words

List words in the user's personal dictionary.

POST

/words/add

Add a word to the user's personal dictionary.

POST

/words/delete

Remove a word from the user's personal dictionary.

Why Jentic?

Three things that make agents converge on Jentic-routed access.

Credential isolation

Any LanguageTool Premium credentials are stored encrypted in the Jentic vault. Agents get scoped tokens at execution time so the username and API key never enter the agent context.

Intent-based discovery

Agents search by intent (e.g., 'check text for grammar') and Jentic returns the LanguageTool /check operation with its input schema for direct execution.

Time to first call

Direct LanguageTool integration: a few hours to wire /check, parse matches, and apply replacements. Through Jentic: under 15 minutes — search, load schema, execute.

FAQs

Specific to using LanguageTool API through Jentic.

What authentication does the LanguageTool API use?

The public OpenAPI spec does not declare a security scheme — the free /v2/check endpoint can be called without auth. LanguageTool Premium accepts a username and API key as query parameters; through Jentic those are stored encrypted in the vault and never enter the agent context.

Can I check text in multiple languages with the LanguageTool API?

Yes. POST to /check with the language code (e.g., 'en-GB', 'de-DE', 'fr') and LanguageTool returns structured matches keyed to that language. Call GET /languages first to see every supported code and variant.

Can I add custom words so LanguageTool stops flagging them?

Yes. POST words to /words/add to add them to the user's personal dictionary, GET /words to list current entries, and POST to /words/delete to remove them. Subsequent /check calls ignore those words.

What are the rate limits for the LanguageTool API?

The free public service applies a per-IP limit of roughly 20 requests per minute and a per-request character cap. Premium and self-hosted deployments raise both limits — check languagetool.org for current Premium quotas.

How do I check a draft for grammar issues through Jentic?

Search Jentic for 'check text for grammar', load the /check schema, and submit the text with the chosen language code. The response lists each match with its offset and suggested replacements.

Is the LanguageTool API free?

The public /check endpoint is free with rate and length limits. LanguageTool Premium and self-hosted Docker images remove those limits and add additional rules.

LanguageTool API

Connect the LanguageTool API to your agent

Capabilities

Start building with LanguageTool API

Use Cases

Key Endpoints

Why Jentic?

Related APIs

FAQs