Datamuse
Datamuse operates a word-finding query engine and lexical search service for developers, educators, and creative-writing applications. The Datamuse API exposes a /words endpoint that finds words matching a rich combination of semantic, phonetic, orthographic, and vocabulary constraints (means-like, sounds-like, spelled-like, synonyms, antonyms, hypernyms, meronyms, triggers, rhymes, homophones, and more) plus a /sug autocomplete endpoint. Free for non-commercial use up to 100,000 requests per day with no API key required; commercial use, custom vocabularies, and higher rate limits are available via a paid commercial agreement. Datamuse also runs OneLook, OneLook Thesaurus, RhymeZone, Rimar.io, and CivicSearch — consumer-facing word search tools built on the same lexical infrastructure.
Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.
API Evangelist profiles Datamuse the way a machine reads it — 51 machine-readable artifacts across 2 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Datamuse scores 57.1/100 (developing), with a separate agent-readiness read of 39/100 (agent aware). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.
Kin Score
How this is scored →scored 2026-07-27 · rubric v0.5
How we profile Datamuse
Each block below is one kind of artifact we hold for Datamuse. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 2
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Datamuse Suggestions API
Autocomplete suggestions with spelling correction and semantic fallback.
Datamuse Words API
Word-finding queries combining semantic, phonetic, orthographic, and vocabulary constraints.
Open Collections 1
Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
Datamuse API
OPEN COLLECTIONPricing Plans 1
Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the six things the Kin Score reads for commercial clarity.
Published pricing tiers and plan structures.
Rate Limits 1
Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.
Documented rate limits and quota policies.
Datamuse Rate Limits
RATE LIMITSFinOps 1
Cost, billing, and metering signals let a buyer model the financial operations of an API before it's live. We profile them for the same reason we profile pricing: the money is part of the contract.
Cost, billing, and metering signals for API financial operations.
Datamuse Finops
FINOPSFeatures 11
The notable capabilities this provider advertises, captured as structured features so they can be searched and compared instead of read one landing page at a time.
Notable capabilities this provider offers.
Means Like (ml)
Reverse-dictionary semantic constraint finding words whose meaning matches an input string of any length.
Sounds Like (sl)
Phonetic constraint returning words pronounced similarly to a given input using a text-to-phonemes algorithm.
Spelled Like (sp)
Orthographic constraint with wildcard pattern matching (* for any chars, ? for a single char).
Predefined Relations (rel_*)
Twelve lexical relations including synonyms, antonyms, hypernyms, hyponyms, holonyms, meronyms, triggers, frequent followers/predecessors, rhymes, near-rhymes, homophones, and c...
Context Ranking
Topics, left-context (lc), and right-context (rc) parameters skew results toward a document theme or surrounding words.
Lexical Metadata (md)
Optional metadata flags add definitions, parts of speech, syllable counts, pronunciations, and corpus frequency to each word.
Pronunciation Formats
Default Arpabet pronunciations or IPA via the ipa flag, drawing on the CMU Pronouncing Dictionary.
Multilingual Vocabularies
Default English (550k terms) and Spanish (500k terms) vocabularies; custom domain vocabularies available on request.
Autocomplete (/sug)
Intelligent prefix suggestions with spelling correction and semantic fallback when exact matches are unavailable.
No API Key Required
Free non-commercial use up to 100,000 requests per day without an account or API token; HTTPS and HTTP both supported.
Query Echo (qe)
Prepends the result list with a record describing the query string, useful for one-shot word-metadata lookups.
Scroll within the panel for all 11 ·
Semantic Vocabularies 1
JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.
JSON-LD contexts and semantic vocabularies used across these APIs.
Datamuse Context
JSON-LDSpectral Rules 2
Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.
Datamuse API Rules
SPECTRALDatamuse API Rules
SPECTRALJSON Schema 2
Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.
Standalone JSON Schema definitions for this provider's data models.
Datamuse Suggestion
JSON SCHEMADatamuse Word
JSON SCHEMAJSON Structure 2
JSON Structure captures the data shapes in a form built for tooling — a complement to JSON Schema that keeps the model machine-legible.
JSON Structure definitions describing this provider's data shapes.
Datamuse Suggestion Structure
JSON STRUCTUREDatamuse Word Structure
JSON STRUCTUREExamples 2
Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.
Example request and response payloads for these APIs.
Datamuse Getwords Example
EXAMPLESecurity Posture 1
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Use Cases 8
What developers actually build with this provider — captured so the catalogue answers 'what is this for', not just 'what does this expose'.
What developers build with this provider.
Vocabulary Building Apps
Power flashcards, quizzes, and language-learning apps with synonyms, antonyms, and related-word lookups.
Creative Writing Tools
Drive rhyme finders, thesaurus add-ins, and reverse-dictionary lookups for poetry, songwriting, and copywriting.
Word Games and Puzzles
Generate clues, fill patterns with sp wildcards, and validate word lists for crosswords, hangman, and word ladders.
Autocomplete and Type-Ahead
Provide intelligent prefix suggestions with spelling correction in search bars and form fields.
Educational Software
Add definitions, syllable counts, and pronunciations to reading apps, ESL tools, and accessibility software.
Search Query Expansion
Expand a user's search terms with semantically related words to improve recall in document or product search.
NLP Pre-Processing
Look up word relations, frequencies, and pronunciations as features for downstream NLP pipelines.
Brand and Product Naming
Combine sounds-like, means-like, and spelled-like constraints to brainstorm brand, domain, or product names.
Scroll within the panel for all 8 ·
Integrations 12
Pre-built integrations with other platforms tell you where this provider already fits in a stack.
Pre-built integrations with other platforms and tools.
OneLook
Datamuse's flagship word search engine indexing 10M+ words across 1000+ dictionaries; built on the same backend.
OneLook Thesaurus
Reverse-dictionary and thesaurus product available on web, as a Google Docs add-on, and as an iOS/Mac app.
RhymeZone
Rhyming dictionary and writing tool partnered with Merriam-Webster, available on web and mobile.
Rimar.io
Spanish-language rhyming dictionary and thesaurus powered by Datamuse's Spanish vocabulary.
CivicSearch
Local government meeting search engine covering 700+ jurisdictions across the US and Canada.
WordNet 3.0
Princeton lexical database supplying synonyms, antonyms, hypernyms, hyponyms, holonyms, and meronyms.
CMU Pronouncing Dictionary
Source for Arpabet pronunciations and the basis for phonetic constraints (sl, rel_rhy, rel_hom, rel_cns).
Google Books Ngrams
Corpus underpinning frequency scores and the rel_jja, rel_jjb, rel_bga, rel_bgb statistical relations.
Wiktionary
Source of definitions returned via the md=d metadata flag.
word2vec / Paraphrase Database
Corpus and embedding sources contributing to means-like and trigger relations.
Obsidian Wordy Plugin
Community plugin embedding Datamuse-powered thesaurus and reverse-dictionary directly into Obsidian.
Model Context Protocol Servers
Multiple community MCP servers (lacausecrypto/datamuse-mcp, pipeworx-io/mcp-datamuse, bhayanak/datamuse-mcp-server) expose the API to LLM agents.
Scroll within the panel for all 12 ·
Solutions 3
Packaged solutions the provider offers on top of the raw API surface.
Packaged solutions this provider offers.
Free Non-Commercial Tier
Up to 100,000 requests per day with no API key, no signup, suitable for prototypes, hobby projects, research, and non-commercial education.
Commercial Plan
Custom contract for production traffic in customer-facing applications, higher quotas, custom vocabularies, and SLA — pricing on request.
Custom Vocabulary Hosting
Domain-specific term lists (medical, legal, gaming, internal jargon) hosted on Datamuse infrastructure with all standard relations.
Resources
Every other property we hold for Datamuse — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Documentation 2
Reference material describing how the API behaves
Agent Surfaces 1
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 2
Pagination, idempotency, versioning, errors, and events
Build 14
SDKs, sample code, and the tooling you integrate with
Scroll within the panel for all 14 ·
Access & Security 1
Authentication, authorization, and security posture
Operate 2
Status, limits, changes, and where to get help
Commercial 5
Pricing, plans, and the legal terms of use
Company 1
The organization behind the API
Other 1
Properties that don't map to a standard resource type
← All providers · Data indexed from github.com/api-evangelist/datamuse · machine-readable index on apis.io