Grammarly vs. Document Intelligence Tools: What Each Actually Checks

Grammarly is a writing assistant. Document intelligence is a quality analysis system. Both find problems in documents, but they find different kinds of problems, and conflating them creates blind spots.

What Grammarly and similar tools check

Writing assistants like Grammarly, ProWritingAid, and similar tools are designed to improve the quality of prose at the sentence level. They check:

**Grammar and mechanics.** Subject-verb agreement, incorrect tense, article misuse, pronoun reference. These are standard grammar rules applied sentence by sentence.

**Spelling.** Misspellings, wrong homophones (their/there/they're), and typos.

**Style.** Passive voice, wordiness, redundancy, informal language in formal contexts. These recommendations are stylistic rather than prescriptive — they suggest rather than correct.

**Clarity.** Sentence-level clarity suggestions: sentences that are too long, clauses that are ambiguous, constructions that are hard to parse.

**Tone.** Some tools offer tone detection — whether a message reads as confident, formal, friendly, or otherwise.

These are genuinely valuable checks. They catch errors that spell-checkers miss and provide suggestions that improve the reader experience. For everyday professional writing — emails, reports, internal memos — a writing assistant is a useful tool.

What writing assistants do not check

Writing assistants operate at the sentence level. They do not analyse the document as a whole.

**Cross-document consistency.** A writing assistant does not know that "Customer" in paragraph 3 and "Client" in paragraph 17 may refer to the same entity. It does not flag terminology drift.

**Internal reference resolution.** It does not know that "see Section 4.2" refers to a section that does not exist.

**Numerical consistency.** It does not verify that the total in the executive summary matches the table in the appendix.

**Date coherence.** It does not check that the effective date precedes the expiry date, or that dates are stated consistently throughout.

**Structural completeness.** It does not detect that a defined term is never used, or that an appendix is referenced but not included.

**Logical contradiction.** It does not identify that two paragraphs make incompatible claims about the same subject.

These are the document-level problems that create legal, financial, and operational risk. They are invisible to a sentence-level tool.

What document intelligence tools check

Document intelligence tools analyse the document as a whole. They check:

• Numerical anomalies: values that are statistically inconsistent with their context
• Date inconsistencies: conflicting or impossible dates
• Internal contradictions: statements that are logically incompatible
• Terminology drift: the same concept referred to differently across the document
• Missing references: internal references that do not resolve
• Duplicate content: passages that are substantially identical
• Placeholder text: markers from the drafting process that were not removed
• Hedge language: obligatory statements expressed permissively
• Reading complexity: the match between the document's difficulty and its intended audience

These are structural and semantic properties of the document that require whole-document analysis.

The gap in the middle

The tools operate at different levels, and there is a gap between them.

Writing assistants do not catch document-level problems. Document intelligence tools do not catch sentence-level grammar errors. A document reviewed by both is more thoroughly checked than a document reviewed by either one alone.

The practical recommendation: use a writing assistant for the prose quality of every professional document, and use a document intelligence tool for structural and consistency checks on any document where accuracy matters — contracts, policies, financial reports, technical specifications, proposals.

A note on AI writing tools

The emergence of AI writing tools (ChatGPT for drafting, Grammarly's AI suggestions, and similar) adds another layer. These tools can improve sentence quality and suggest structural revisions. But they do not inherently check a document's internal consistency, validate its numerical accuracy, or verify that its references resolve.

Document quality requires checking the document against itself — comparing what section 4 says to what section 12 says, verifying that figures agree across the document, confirming that all cross-references resolve. That is analysis, not writing. It requires a different kind of tool.