Apache OpenNLP website screenshot

Apache OpenNLP

Apache OpenNLP is a machine learning based toolkit for the processing of natural language text. It supports common NLP tasks such as tokenization, sentence segmentation, part-of-speech tagging, named entity extraction, chunking, parsing, and coreference resolution.

Apache OpenNLP publishes 10 APIs on the APIs.io network, including Chunking API, Document Categorization API, Language Detection API, and 7 more. Tagged areas include Machine Learning, Natural Language Processing, NLP, Text Processing, and Apache.

The Apache OpenNLP catalog on APIs.io includes 1 JSON-LD context and 2 Spectral governance rulesets.

Apache OpenNLP’s developer surface includes documentation, getting-started guide, engineering blog, and 7 more developer resources.

🌐 Visit website 📡 Source on GitHub
42.7/100 developing ▼ -9.1 Agent 22/100 agent aware Full breakdown ↓
scored 2026-07-28 · rubric v0.6
AccessFreemium
10 APIs 10 Features 5 Use Cases
Machine LearningNatural Language ProcessingNLPText ProcessingApacheOpen SourceJava

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-28 · rubric v0.6
Composite quality — 42.7/100 · developing
Contract Quality 10.9 / 25
Developer Ergonomics 4.3 / 20
Commercial Clarity 7.9 / 20
Operational Transparency 4.8 / 13
Governance 8.3 / 12
Discoverability 6.5 / 10
Agent readiness — 22/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 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
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/apache-opennlp: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 10

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

Apache OpenNLP Chunking API

The Chunking API from Apache OpenNLP — 1 operation(s) for chunking.

Apache OpenNLP Document Categorization API

The Document Categorization API from Apache OpenNLP — 1 operation(s) for document categorization.

Apache OpenNLP Language Detection API

The Language Detection API from Apache OpenNLP — 1 operation(s) for language detection.

Apache OpenNLP Lemmatization API

The Lemmatization API from Apache OpenNLP — 1 operation(s) for lemmatization.

Apache OpenNLP Models API

The Models API from Apache OpenNLP — 2 operation(s) for models.

Apache OpenNLP Named Entity Recognition API

The Named Entity Recognition API from Apache OpenNLP — 1 operation(s) for named entity recognition.

Apache OpenNLP Parsing API

The Parsing API from Apache OpenNLP — 1 operation(s) for parsing.

Apache OpenNLP POS Tagging API

The POS Tagging API from Apache OpenNLP — 1 operation(s) for pos tagging.

Apache OpenNLP Sentence Detection API

The Sentence Detection API from Apache OpenNLP — 1 operation(s) for sentence detection.

Apache OpenNLP Tokenization API

The Tokenization API from Apache OpenNLP — 1 operation(s) for tokenization.

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Pricing Plans 1

Published pricing tiers and plan structures.

Apache Opennlp Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Apache Opennlp Rate Limits

5 limits

RATE LIMITS

FinOps 1

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

Apache Opennlp Finops

FINOPS

Features 10

Notable capabilities this provider offers.

Language Detection

Detects document language using ISO-639-3 classification

Sentence Detection

Splits text into individual sentences with character offsets

Tokenization

Segments text into words and punctuation with position tracking

Named Entity Recognition

Detects persons, locations, organizations, and other named entities

POS Tagging

Assigns Penn Treebank POS tags to each token

Lemmatization

Reduces tokens to their dictionary base forms

Chunking

Identifies noun phrases, verb phrases, and other syntactic chunks

Parsing

Builds full syntactic parse trees using constituency parsing

Document Categorization

Classifies documents into predefined categories

Custom Model Training

Train custom models with Maxent, Perceptron, or Naive Bayes algorithms

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Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Apache Opennlp Context

18 classes · 24 properties

JSON-LD

Spectral Rules 2

Spectral governance rulesets for linting and validating these APIs.

Apache OpenNLP API Rules

5 rules · 3 warnings 2 info

SPECTRAL

Apache OpenNLP API Rules

16 rules · 5 errors 9 warnings 2 info

SPECTRAL

JSON Schema 18

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

CategorizationResult

2 properties

JSON SCHEMA

Chunk

4 properties

JSON SCHEMA

ChunkingResult

1 properties

JSON SCHEMA

LanguageDetectionResult

3 properties

JSON SCHEMA

LanguageProbability

2 properties

JSON SCHEMA

LemmatizationResult

2 properties

JSON SCHEMA

ModelInfo

5 properties

JSON SCHEMA

ModelList

1 properties

JSON SCHEMA

NamedEntity

5 properties

JSON SCHEMA

NERResult

1 properties

JSON SCHEMA

ParseResult

2 properties

JSON SCHEMA

POSTaggingResult

3 properties

JSON SCHEMA

POSTokensRequest

2 properties

JSON SCHEMA

SentenceDetectionResult

2 properties

JSON SCHEMA

Span

3 properties

JSON SCHEMA

TextRequest

3 properties

JSON SCHEMA

TokenizationResult

3 properties

JSON SCHEMA

TokensRequest

2 properties

JSON SCHEMA

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JSON Structure 18

JSON Structure definitions describing this provider's data shapes.

Apache Opennlp Categorization Result Structure

2 properties

JSON STRUCTURE

Apache Opennlp Chunk Structure

4 properties

JSON STRUCTURE

Apache Opennlp Chunking Result Structure

1 properties

JSON STRUCTURE

Apache Opennlp Language Detection Result Structure

3 properties

JSON STRUCTURE

Apache Opennlp Language Probability Structure

2 properties

JSON STRUCTURE

Apache Opennlp Lemmatization Result Structure

2 properties

JSON STRUCTURE

Apache Opennlp Model Info Structure

5 properties

JSON STRUCTURE

Apache Opennlp Model List Structure

1 properties

JSON STRUCTURE

Apache Opennlp Named Entity Structure

5 properties

JSON STRUCTURE

Apache Opennlp Ner Result Structure

1 properties

JSON STRUCTURE

Apache Opennlp Parse Result Structure

2 properties

JSON STRUCTURE

Apache Opennlp Pos Tagging Result Structure

3 properties

JSON STRUCTURE

Apache Opennlp Pos Tokens Request Structure

2 properties

JSON STRUCTURE

Apache Opennlp Sentence Detection Result Structure

2 properties

JSON STRUCTURE

Apache Opennlp Span Structure

3 properties

JSON STRUCTURE

Apache Opennlp Text Request Structure

3 properties

JSON STRUCTURE

Apache Opennlp Tokenization Result Structure

3 properties

JSON STRUCTURE

Apache Opennlp Tokens Request Structure

2 properties

JSON STRUCTURE

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Examples 18

Example request and response payloads for these APIs.

Apache Opennlp Categorization Result Example

2 fields

EXAMPLE

Apache Opennlp Chunk Example

4 fields

EXAMPLE

Apache Opennlp Chunking Result Example

1 fields

EXAMPLE

Apache Opennlp Language Detection Result Example

3 fields

EXAMPLE

Apache Opennlp Language Probability Example

2 fields

EXAMPLE

Apache Opennlp Lemmatization Result Example

2 fields

EXAMPLE

Apache Opennlp Model Info Example

5 fields

EXAMPLE

Apache Opennlp Model List Example

1 fields

EXAMPLE

Apache Opennlp Named Entity Example

5 fields

EXAMPLE

Apache Opennlp Ner Result Example

1 fields

EXAMPLE

Apache Opennlp Parse Result Example

2 fields

EXAMPLE

Apache Opennlp Pos Tagging Result Example

3 fields

EXAMPLE

Apache Opennlp Pos Tokens Request Example

2 fields

EXAMPLE

Apache Opennlp Sentence Detection Result Example

2 fields

EXAMPLE

Apache Opennlp Span Example

3 fields

EXAMPLE

Apache Opennlp Text Request Example

3 fields

EXAMPLE

Apache Opennlp Tokenization Result Example

3 fields

EXAMPLE

Apache Opennlp Tokens Request Example

2 fields

EXAMPLE

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Security Posture 2

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

Apache Opennlp Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Apache Opennlp Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

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

Apache Opennlp Agentic Access

11 operations · 9 acting

11 operations · 9 acting

AGENTIC

Use Cases 5

What developers build with this provider.

Information Extraction

Extract structured data from unstructured text documents

Text Classification

Automatically categorize documents by topic or sentiment

Search Enhancement

Improve search relevance with NLP-based query processing

Content Analysis

Analyze large text corpora for entities, topics, and patterns

Chatbot Development

Build conversational AI with NLP intent and entity extraction

Integrations 5

Pre-built integrations with other platforms and tools.

Apache Solr

Integrate OpenNLP with Apache Solr for NLP-enhanced search

Apache Lucene

Use OpenNLP analyzers in Lucene text processing pipelines

Apache Flink

Real-time NLP processing with Apache Flink data streams

UIMA

Apache UIMA framework integration for unstructured information analysis

Maven/Gradle

Available on Maven Central for Java build system integration

Resources

Get Started 1

Portal, sign-up, and the first successful call

GettingStarted
GettingStarted

Documentation 1

Reference material describing how the API behaves

Documentation
Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess
AgenticAccess

Design & Contract 3

Pagination, idempotency, versioning, errors, and events

SpectralRules
SpectralRules
 Vocabulary
Vocabulary
 JSONLD
JSONLD

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization

Access & Security 2

Authentication, authorization, and security posture

VulnerabilityDisclosure
VulnerabilityDisclosure
 DomainSecurity
DomainSecurity

Company 1

The organization behind the API

Blog
Blog

Source (apis.yml)

apis.yml Raw ↑ 
aid: apache-opennlp
name: Apache OpenNLP
description: Apache OpenNLP is a machine learning based toolkit for the processing of natural language text. It supports common
  NLP tasks such as tokenization, sentence segmentation, part-of-speech tagging, named entity extraction, chunking, parsing,
  and coreference resolution.
type: Index
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: Consumer
access: 3rd-Party
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/apache-opennlp.png
tags:
- Machine Learning
- Natural Language Processing
- NLP
- Text Processing
- Apache
- Open Source
- Java
created: '2026-03-16'
modified: '2026-05-19'
url: https://raw.githubusercontent.com/api-evangelist/apache-opennlp/refs/heads/main/apis.yml
specificationVersion: '0.19'
apis:
- aid: apache-opennlp:apache-opennlp-chunking-api
  name: Apache OpenNLP Chunking API
  description: The Chunking API from Apache OpenNLP — 1 operation(s) for chunking.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Chunking
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-chunking-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-document-categorization-api
  name: Apache OpenNLP Document Categorization API
  description: The Document Categorization API from Apache OpenNLP — 1 operation(s) for document categorization.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Document Categorization
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-document-categorization-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-language-detection-api
  name: Apache OpenNLP Language Detection API
  description: The Language Detection API from Apache OpenNLP — 1 operation(s) for language detection.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Language Detection
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-language-detection-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-lemmatization-api
  name: Apache OpenNLP Lemmatization API
  description: The Lemmatization API from Apache OpenNLP — 1 operation(s) for lemmatization.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Lemmatization
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-lemmatization-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-models-api
  name: Apache OpenNLP Models API
  description: The Models API from Apache OpenNLP — 2 operation(s) for models.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Models
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-models-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-named-entity-recognition-api
  name: Apache OpenNLP Named Entity Recognition API
  description: The Named Entity Recognition API from Apache OpenNLP — 1 operation(s) for named entity recognition.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Named Entity Recognition
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-named-entity-recognition-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-parsing-api
  name: Apache OpenNLP Parsing API
  description: The Parsing API from Apache OpenNLP — 1 operation(s) for parsing.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Parsing
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-parsing-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-pos-tagging-api
  name: Apache OpenNLP POS Tagging API
  description: The POS Tagging API from Apache OpenNLP — 1 operation(s) for pos tagging.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - POS Tagging
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-pos-tagging-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-sentence-detection-api
  name: Apache OpenNLP Sentence Detection API
  description: The Sentence Detection API from Apache OpenNLP — 1 operation(s) for sentence detection.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Sentence Detection
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-sentence-detection-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
- aid: apache-opennlp:apache-opennlp-tokenization-api
  name: Apache OpenNLP Tokenization API
  description: The Tokenization API from Apache OpenNLP — 1 operation(s) for tokenization.
  humanURL: https://opennlp.apache.org/docs/
  tags:
  - Tokenization
  properties:
  - type: OpenAPI
    url: openapi/apache-opennlp-tokenization-api-openapi.yml
  - type: Documentation
    url: https://opennlp.apache.org/docs/
maintainers:
- FN: Kin Lane
  email: info@apievangelist.com
common:
- type: AgenticAccess
  url: agentic-access/apache-opennlp-agentic-access.yml
- type: VulnerabilityDisclosure
  url: security/apache-opennlp-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/apache-opennlp-domain-security.yml
- type: GitHubOrganization
  url: https://github.com/apache/opennlp
- type: Documentation
  url: https://opennlp.apache.org/
- type: GettingStarted
  url: https://opennlp.apache.org/docs/
- type: SpectralRules
  url: rules/apache-opennlp-spectral-rules.yml
- type: Vocabulary
  url: vocabulary/apache-opennlp-vocabulary.yaml
- type: JSONLD
  url: json-ld/apache-opennlp-context.jsonld
- type: Features
  data:
  - name: Language Detection
    description: Detects document language using ISO-639-3 classification
  - name: Sentence Detection
    description: Splits text into individual sentences with character offsets
  - name: Tokenization
    description: Segments text into words and punctuation with position tracking
  - name: Named Entity Recognition
    description: Detects persons, locations, organizations, and other named entities
  - name: POS Tagging
    description: Assigns Penn Treebank POS tags to each token
  - name: Lemmatization
    description: Reduces tokens to their dictionary base forms
  - name: Chunking
    description: Identifies noun phrases, verb phrases, and other syntactic chunks
  - name: Parsing
    description: Builds full syntactic parse trees using constituency parsing
  - name: Document Categorization
    description: Classifies documents into predefined categories
  - name: Custom Model Training
    description: Train custom models with Maxent, Perceptron, or Naive Bayes algorithms
- type: UseCases
  data:
  - name: Information Extraction
    description: Extract structured data from unstructured text documents
  - name: Text Classification
    description: Automatically categorize documents by topic or sentiment
  - name: Search Enhancement
    description: Improve search relevance with NLP-based query processing
  - name: Content Analysis
    description: Analyze large text corpora for entities, topics, and patterns
  - name: Chatbot Development
    description: Build conversational AI with NLP intent and entity extraction
- type: Integrations
  data:
  - name: Apache Solr
    description: Integrate OpenNLP with Apache Solr for NLP-enhanced search
  - name: Apache Lucene
    description: Use OpenNLP analyzers in Lucene text processing pipelines
  - name: Apache Flink
    description: Real-time NLP processing with Apache Flink data streams
  - name: UIMA
    description: Apache UIMA framework integration for unstructured information analysis
  - name: Maven/Gradle
    description: Available on Maven Central for Java build system integration
- url: https://opennlp.apache.org/feed.xml
  type: Blog