Prelude

Prelude is a phone and email verification API - "the trust layer between your signups and your business." Its Verify API creates and checks one-time passcodes (OTP) across SMS, WhatsApp, RCS, Viber, and voice in 230+ countries, with smart multi-provider routing and built-in anti-fraud. Alongside Verify, Prelude offers Notify (transactional messaging), Lookup / Intel (phone number intelligence - line type, carrier, ported and temporary flags, CNAM), and Watch (anti-fraud risk prediction and feedback). The public REST API v2 lives at https://api.prelude.dev/v2 with Bearer API-key auth and official SDKs for Python, Node.js, Java, and Go. Prelude positions itself as a developer-first alternative to Twilio Verify.

Prelude publishes 4 APIs on the APIs.io network, including Lookup API, Transactional API, Verification API, and 1 more. Tagged areas include Number Verification, Phone Verification, OTP, Authentication, and Anti-Fraud.

Prelude’s developer surface includes authentication, documentation, engineering blog, and 6 more developer resources.

🌐 Visit website 📡 Source on GitHub
35.0/100 thin ▬ flat Agent 31/100 agent aware Full breakdown ↓
scored 2026-08-10 · rubric v0.9.1
AccessPaidSelf serve
4 APIs
Number VerificationPhone VerificationOTPAuthenticationAnti-FraudTwo-Factor AuthenticationSMSPhone Number Lookup

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-10 · rubric v0.9.1
Composite quality — 35.0/100 · thin
Contract Quality 15.9 / 25
Developer Ergonomics 4.3 / 20
Commercial Clarity 7.9 / 20
Operational Transparency 4.1 / 13
Governance 0.0 / 12
Discoverability 7.4 / 10
Agent readiness — 31/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
MCP Server 0 / 12
Machine-Readable Auth 10 / 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/prelude-so: 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 4

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

Prelude Lookup API

Phone number intelligence - line type, carrier, and flags.

Prelude Transactional API

Send transactional messages over SMS, RCS, and WhatsApp.

Prelude Verification API

Create and check one-time passcode (OTP) verifications.

Prelude Watch API

Anti-fraud risk prediction and outcome feedback.

Open Collections 1

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Prelude API v2

OPEN COLLECTION

Pricing Plans 1

Published pricing tiers and plan structures.

Prelude So Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Prelude So Rate Limits

3 limits

RATE LIMITS

FinOps 1

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

Prelude So Finops

FINOPS

Security Posture 1

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

Prelude So Authentication

http · 1 scheme

SECURITY

Agentic Access 1

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

Prelude So Agentic Access

7 operations · 6 acting · 1 human-in-the-loop

7 operations · 6 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation
Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess
AgenticAccess

Access & Security 1

Authentication, authorization, and security posture

Authentication
Authentication

Operate 1

Status, limits, changes, and where to get help

RateLimits
RateLimits

Commercial 2

Pricing, plans, and the legal terms of use

Plans
Plans
 FinOps
FinOps

Company 3

The organization behind the API

LinkedIn
LinkedIn
 Website
Website
 Blog
Blog

Source (apis.yml)

apis.yml Raw ↑ 
aid: prelude-so
url: https://raw.githubusercontent.com/api-evangelist/prelude-so/refs/heads/main/apis.yml
name: Prelude
kind: company
description: Prelude is a phone and email verification API - "the trust layer between your signups and your business." Its
  Verify API creates and checks one-time passcodes (OTP) across SMS, WhatsApp, RCS, Viber, and voice in 230+ countries, with
  smart multi-provider routing and built-in anti-fraud. Alongside Verify, Prelude offers Notify (transactional messaging),
  Lookup / Intel (phone number intelligence - line type, carrier, ported and temporary flags, CNAM), and Watch (anti-fraud
  risk prediction and feedback). The public REST API v2 lives at https://api.prelude.dev/v2 with Bearer API-key auth and official
  SDKs for Python, Node.js, Java, and Go. Prelude positions itself as a developer-first alternative to Twilio Verify.
accessModel:
  pricing: paid
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Paid · Self-serve signup
  confidence: high
  source:
  - plans
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/prelude-so.png
tags:
- Number Verification
- Phone Verification
- OTP
- Authentication
- Anti-Fraud
- Two-Factor Authentication
- SMS
- Phone Number Lookup
created: '2026-07-11'
modified: '2026-07-11'
specificationVersion: '0.19'
apis:
- aid: prelude-so:prelude-so-lookup-api
  name: Prelude Lookup API
  description: Phone number intelligence - line type, carrier, and flags.
  humanURL: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  baseURL: https://api.prelude.dev/v2
  tags:
  - Lookup
  properties:
  - type: OpenAPI
    url: openapi/prelude-so-lookup-api-openapi.yml
  - type: Documentation
    url: https://docs.prelude.so/verify/v2/documentation/introduction
  - type: APIReference
    url: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  - type: PostmanCollection
    url: collections/prelude-so.postman_collection.json
  - type: OpenCollection
    url: collections/prelude-so.opencollection.json
  - type: APIReference
    url: https://docs.prelude.so/intel/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/watch/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/notify/v2/api-reference
- aid: prelude-so:prelude-so-transactional-api
  name: Prelude Transactional API
  description: Send transactional messages over SMS, RCS, and WhatsApp.
  humanURL: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  baseURL: https://api.prelude.dev/v2
  tags:
  - Transactional
  properties:
  - type: OpenAPI
    url: openapi/prelude-so-transactional-api-openapi.yml
  - type: Documentation
    url: https://docs.prelude.so/verify/v2/documentation/introduction
  - type: APIReference
    url: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  - type: PostmanCollection
    url: collections/prelude-so.postman_collection.json
  - type: OpenCollection
    url: collections/prelude-so.opencollection.json
  - type: APIReference
    url: https://docs.prelude.so/intel/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/watch/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/notify/v2/api-reference
- aid: prelude-so:prelude-so-verification-api
  name: Prelude Verification API
  description: Create and check one-time passcode (OTP) verifications.
  humanURL: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  baseURL: https://api.prelude.dev/v2
  tags:
  - Verification
  properties:
  - type: OpenAPI
    url: openapi/prelude-so-verification-api-openapi.yml
  - type: Documentation
    url: https://docs.prelude.so/verify/v2/documentation/introduction
  - type: APIReference
    url: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  - type: PostmanCollection
    url: collections/prelude-so.postman_collection.json
  - type: OpenCollection
    url: collections/prelude-so.opencollection.json
  - type: APIReference
    url: https://docs.prelude.so/intel/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/watch/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/notify/v2/api-reference
- aid: prelude-so:prelude-so-watch-api
  name: Prelude Watch API
  description: Anti-fraud risk prediction and outcome feedback.
  humanURL: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  baseURL: https://api.prelude.dev/v2
  tags:
  - Watch
  properties:
  - type: OpenAPI
    url: openapi/prelude-so-watch-api-openapi.yml
  - type: Documentation
    url: https://docs.prelude.so/verify/v2/documentation/introduction
  - type: APIReference
    url: https://docs.prelude.so/verify/v2/api-reference/create-or-retry-a-verification
  - type: PostmanCollection
    url: collections/prelude-so.postman_collection.json
  - type: OpenCollection
    url: collections/prelude-so.opencollection.json
  - type: APIReference
    url: https://docs.prelude.so/intel/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/watch/v2/api-reference
  - type: APIReference
    url: https://docs.prelude.so/notify/v2/api-reference
common:
- type: AgenticAccess
  url: agentic-access/prelude-so-agentic-access.yml
- type: Authentication
  url: authentication/prelude-so-authentication.yml
- type: LinkedIn
  url: https://www.linkedin.com/company/prelude-so
- type: Website
  url: https://prelude.so
- type: Documentation
  url: https://docs.prelude.so
- type: Plans
  url: plans/prelude-so-plans-pricing.yml
- type: RateLimits
  url: rate-limits/prelude-so-rate-limits.yml
- type: FinOps
  url: finops/prelude-so-finops.yml
- url: https://prelude.so/blog
  type: Blog
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com