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
37.0/100 thin ▬ flat Agent 20/100 agent aware saas Full breakdown ↓
scored 2026-08-30 · rubric v0.17.2
AccessPaidSelf serve
1 APIs
Number VerificationPhone VerificationOTPAuthenticationAnti-FraudTwo-Factor AuthenticationSMSPhone Number Lookup

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-30 · rubric v0.17.2
Composite quality — 37.0/100 · thin
Contract Quality 12.1 / 21
Developer Ergonomics 6.1 / 17
Access Clarity 6.7 / 17
Operational Transparency 3.5 / 11
Contract Governance 0.0 / 10
Discoverability 5.8 / 9
Regulatory Posture 1.2 / 15
Agent readiness — 20/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
Documented Reversibility 0 / 6
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
Delegated User Identity 0 / 6
Protected Resource Metadata 0 / 5
Registration Without a Human 0 / 6
Agentic Commerce Surface 0 / 5
Regulatory Posture applies to this provider. Its tags matched the Telecommunications regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.
The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.
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 6

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

API Collection

OPEN COLLECTION

Prelude Lookup API

OPEN COLLECTION

Prelude Lookup Transactional API

OPEN COLLECTION

Prelude Lookup Verification API

OPEN COLLECTION

Prelude Lookup Watch API

OPEN COLLECTION

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.
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
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: '0.23'
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

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