Service — Text Intelligence

NLP Annotation

High-accuracy text labeling for named entity recognition, intent classification, sentiment analysis, relation extraction, and more. AI pre-labeling cuts annotation time by 40% — human experts validate and correct everything.

40%
Faster annotation via AI pre-labeling with human expert validation
≥0.72
Cohen's kappa minimum on every NLP annotation batch delivered
12+
Supported Indian and international languages
6
Core NLP annotation task types with domain-specialist annotators
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Named Entity RecognitionIntent ClassificationSentiment AnalysisRelation ExtractionCoreference ResolutionText ClassificationDependency ParsingSemantic Role LabelingNamed Entity RecognitionIntent ClassificationSentiment AnalysisRelation ExtractionCoreference ResolutionText Classification
What It Is

Structured text labels that teach machines to understand language

NLP annotation is the process of adding structured labels to raw text so that machine learning models can learn linguistic patterns. Every search engine, chatbot, document processor, and voice assistant relies on millions of carefully annotated text examples to understand what human language means.

When your NLP model reads a sentence like "Dr. Arora at Apollo Hospital prescribed metformin for diabetes management," it needs to have learned — from thousands of labeled examples — that "Dr. Arora" is a PERSON, "Apollo Hospital" is an ORGANISATION, "metformin" is a MEDICATION, and "diabetes" is a CONDITION. That learning comes entirely from annotation.

The challenge is that NLP annotation is deceptively difficult. For a general-purpose model, "Apple" can be a fruit, a company, or a person's name — and only context determines which. For a medical model, understanding whether "cold" is a symptom, a temperature, or a descriptor requires clinical knowledge that a non-expert annotator simply does not have.

Concave AI's NLP annotation combines an AI pre-labeling layer (which handles the clear, unambiguous cases quickly) with domain-specialist human annotators who handle every ambiguous case, entity boundary decision, and domain-specific judgment call. The result is datasets with the speed advantage of AI pre-labeling and the accuracy guarantee of expert human review.

What is AI pre-labeling and why does it matter?
Before human annotators see a document, our NLP pipeline runs it through a pre-annotation model that proposes labels for clear cases. Annotators then confirm or correct these suggestions rather than labeling from scratch. Studies show this reduces annotation time by 35–50% with no decrease in quality — as long as the human remains the final decision-maker, not just a rubber stamp for AI suggestions.
Why does domain expertise matter for NLP annotation?
Clinical NLP requires annotators who can distinguish "left bundle branch block" (a cardiac condition) from "left" as a directional term. Legal NLP requires annotators who understand the difference between a "party" (legal entity in a contract) and the general use of the word. Financial NLP requires annotators who can correctly tag regulatory citations, instrument names, and risk categories. General crowdworkers produce systematically low-quality data for these domains regardless of guideline quality.
NLP Named Entity Recognition
● PERSON ENTITY
● ORGANIZATION
● LOCATION
● DATE / AMOUNT
▼ ENTITY TYPES DETECTED
PERSON
ORG
LOC
DATE
AMOUNT
✓ 38,420 ENTITIES TAGGED
Language Understanding

Annotation that understands context, not just tokens

NLP annotation requires human linguists who understand pragmatics, irony, and domain-specific terminology. Our annotators are trained on your domain before touching a single label.

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Live Annotation Interface

Named Entity Recognition Labelling Tool

Domain-specialist annotators tag entities across legal, medical, financial, and news corpora — building training sets for production NER models.

ConcaveLabel Studio — NER Annotation · Corpus: SEBI Enforcement Orders · 14,820 sentences

Rajesh Kumar Mehta, former CFO of Infotech Ventures Ltd., was found by SEBI to have made undisclosed trades on March 14, 2023 prior to the merger announcement with Bharti Digital Solutions. The total gain was estimated at ₹4.2 crore.

The order, issued from the SEBI Mumbai Regional Office, imposes a ₹1.8 crore penalty and bars Mehta from securities markets for 3 years effective 01 April 2024.

Counsel Adv. Sunita Rao of Rao & Pillai Associates, New Delhi, filed an appeal at the Securities Appellate Tribunal citing procedural violations under Regulation 4(2)(g).

ENTITY TYPES
PERSON
ORGANIZATION
LOCATION
DATE
AMOUNT
REGULATION
Task Types

Six core NLP tasks, each with specialist annotators

We do not use a one-size-fits-all annotator pool. Each task type is matched to the appropriate domain expert to ensure annotation accuracy exceeds what guidelines alone can achieve.

🏷
Named Entity Recognition (NER)
Identifying and classifying named entities — persons, organisations, locations, dates, products, medical terms, legal references — within text. We support standard ontologies (CoNLL, OntoNotes) and custom entity schemas for your domain.
CoNLL formatCustom schemasNested entities
🎯
Intent Classification
Labeling utterances with the user's underlying intent for conversational AI, chatbot, and voice assistant training. We handle single-label, multi-label, and hierarchical intent taxonomies. Slot filling for entity extraction from intents also supported.
Multi-labelHierarchicalSlot filling
💬
Sentiment Analysis
Document-level, sentence-level, and aspect-level sentiment classification. Beyond positive/negative/neutral — fine-grained emotion detection, sentiment intensity scoring, and domain-specific sentiment (e.g., financial sentiment for earnings call transcripts is different from product review sentiment).
Aspect-levelFine-grainedDomain-specific
🔗
Relation Extraction
Identifying semantic relationships between entities — "works_at," "prescribed_by," "subsidiary_of," "causes." Critical for knowledge graph construction, medical record structuring, and contract analysis. We support both closed and open information extraction formats.
Knowledge graphsMedical REOpen IE
👥
Coreference Resolution
Linking all mentions of the same entity across a document — "the company," "it," "Apple," "the tech giant" all referring to one entity. Essential for document understanding, summarisation models, and question-answering systems that need to track entities across long contexts.
Pronoun resolutionEntity linkingCross-sentence
📁
Text Classification
Multi-class and multi-label categorisation of documents, paragraphs, or sentences. Topic classification, toxicity detection, language identification, readability scoring, compliance flagging. Custom taxonomy design included — we work with your team to define the right label set for your use case.
Multi-classToxicity detectionCustom taxonomy
The Process

From raw text to verified annotation dataset

Our NLP annotation pipeline is built to prevent the two most common failure modes: annotator inconsistency and domain knowledge gaps. Both are addressed structurally, not just through guidelines.

01
Data Audit & Taxonomy Design
We review a sample of your raw text data (typically 200–500 documents) to understand language complexity, domain vocabulary, ambiguity distribution, and edge case frequency. From this, we design the annotation taxonomy — entity types, relation types, or classification labels — with explicit boundary rules for ambiguous cases. For each label, we write 5–10 positive and 3–5 negative examples with explanations. This taxonomy is approved by your team before annotation begins.
Data sample reviewTaxonomy designBoundary rulesClient sign-off
02
AI Pre-Labeling Pipeline
Our NLP preprocessing pipeline runs your documents through a pre-annotation model tuned to your task type. For NER, we use a combination of dictionary matching, SpaCy transformer models, and LLM-assisted labeling to propose entity spans. For classification tasks, a fine-tuned BERT/RoBERTa model generates probability-weighted label suggestions. All pre-labels are marked with confidence scores — high-confidence labels require only quick validation; low-confidence labels trigger full human review. This reduces raw annotation time by 35–45%.
SpaCy + transformer pre-labelingConfidence scoring35–45% time reduction
03
Domain-Expert Human Annotation
Calibrated domain specialists annotate your data using our annotation platform. Annotators see pre-label suggestions but are not bound by them. Gold standard documents (with pre-verified correct labels) are injected at a 6% rate to monitor annotator accuracy in real time. Daily kappa tracking across the annotator pool catches individual annotator drift immediately. Ambiguous cases are flagged for adjudication by a senior annotator. We do not allow annotation velocity to compromise kappa — slow annotators who annotate carefully are preferable to fast annotators who drift.
Expert domain annotators6% gold injectionDaily kappa monitoringAmbiguity adjudication
04
Three-Tier Quality Assurance
Tier 1: Automated schema validation and anomaly detection (missing required labels, suspiciously fast completion, unusual label distributions). Tier 2: 15% random sample independently re-annotated by a second expert; F1 score calculated against original annotation. Tier 3: ML-engineer review of 5% sample plus all flagged documents. Any batch where cross-annotator F1 falls below 0.88 is returned for reannotation before delivery.
Auto schema validation15% peer re-annotationF1 ≥ 0.88 gateML-engineer review
05
Delivery & Benchmark Follow-Up
Delivery in your requested format: CoNLL-2003, IOB2, BRAT, JSONL, CSV, or spaCy DocBin. Includes full QA report with per-annotator kappa, F1, and precision/recall by label type, plus a data card. Two weeks post-delivery, we follow up on your model's NER/classification performance metrics — and use those results to refine annotation guidelines for your next batch.
CoNLL / IOB2 / JSONL / BRATPer-label F1 reportData cardBenchmark follow-up
What You Get

Annotated datasets backed by verifiable quality proof

📦
Annotated Dataset
Labeled data in your preferred format: CoNLL-2003, IOB2, BRAT standoff, JSONL, CSV, or spaCy DocBin. Each document includes annotation spans, label types, annotator IDs, confidence flags, and adjudication decisions for resolved disagreements.
📊
QA Report
Per-annotator kappa and F1 by label type, gold standard accuracy, disagreement log with adjudication decisions, label distribution statistics, and entity boundary consistency analysis. Every metric verifiable against raw annotation logs.
🗂
Data Card & Annotation Guide
ML data card with annotator profiles, label definitions, known ambiguities, out-of-scope cases, and quality thresholds applied. The full annotation guideline document is included so future annotators or reviewers can audit any label decision.
Common Questions

What teams ask before starting

Which Indian languages do you support for NLP annotation?
We have active annotator pools for Hindi, Marathi, Tamil, Telugu, Kannada, Bengali, Malayalam, and Gujarati, in addition to English. For code-mixed text (Hinglish, Tanglish) we have specialist annotators who are native speakers of the relevant base languages. For other Indian languages, we can typically recruit qualified annotators within 2–3 weeks.
Can you handle domain-specific entity types not in standard ontologies?
Yes — and this is one of our core strengths. We design custom taxonomies for every project. For a pharmaceutical client, we might define DRUG_GENERIC, DRUG_BRAND, DOSAGE, FREQUENCY, ROUTE_OF_ADMINISTRATION, and ADVERSE_EVENT as custom entity types with precise boundary rules. We treat taxonomy design as part of the engagement, not an afterthought, because the entity schema is often the hardest part to get right.
What is a realistic timeline for a 10,000 document NLP annotation project?
With AI pre-labeling and a team of 5–8 expert annotators, a 10,000-document NER project typically takes 3–5 weeks for production annotation plus 1 week for QA review. Complex tasks (multi-layer annotation with relations and coreference) take longer. We provide a detailed timeline estimate after reviewing your data sample in scoping — we do not give generic estimates without seeing your actual document complexity.
Pricing

Per-document
transparent pricing

NLP annotation is priced per document based on task complexity, document length, and domain. Volume discounts apply at 5,000+ documents.

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Basic NER / sentiment (short docs)₹100–200 / doc
Multi-label classification₹150–300 / doc
Complex NER + relations₹250–400 / doc
Medical / legal / finance NLP₹300–600 / doc
Coreference resolution₹200–400 / doc
Minimum project size500 documents

Get a free NLP annotation baseline

Send us 100 text samples from your domain. We will annotate them with our expert team and return a kappa report and label distribution analysis — at no cost.