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 API contracts indexed 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 Fraud Prevention.

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

🌐 Visit website 📡 Profile data on GitHub

26.1/100 emerging ▬ flat Agent 20/100 agent aware Front door AI 3/6 light saas Full breakdown ↓
scored 2026-10-31 · rubric v0.25.0 · Show this score on your site →

AccessPaid

1 published contract

Number Verification Phone Verification OTP Authentication Fraud Prevention Two-Factor Authentication SMS Phone Number Lookup

Kin Score

Kin Score How this is scored →
scored 2026-10-31 · rubric v0.25.0

Composite quality — 26.1/100 · emerging

Contract Quality 10.9 / 21

Developer Ergonomics 5.5 / 17

Access Clarity 1.3 / 17

Operational Transparency 0.9 / 11

Contract Governance 0.0 / 10

Discoverability 5.6 / 9

Regulatory Posture 0.8 / 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 Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

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.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

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/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented)

9 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Access Clarity scores 7.9 — up to +18.4 composite points
Developer Ergonomics scores 32.1 — up to +13.6 composite points
Contract Quality scores 51.1 — up to +12.2 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/prelude-so/apis.yml: open an issue on github.com/api-evangelist/prelude-so to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

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 5

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

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

Website

Website

Blog

Blog

Source (apis.yml)

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: unknown
  trial: false
  try_now: false
  public: false
  label: Paid
  confidence: medium
  source:
  - plans
  - authentication
  generated: '2026-09-03'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/prelude-so.png
x-docs-platform: mintlify
x-docs-platform-confidence: medium
x-docs-platform-checked: 2026-10-04
x-docs-hosting: vercel
tags:
- Number Verification
- Phone Verification
- OTP
- Authentication
- Fraud Prevention
- Two-Factor Authentication
- SMS
- Phone Number Lookup
tags_raw:
- 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

Prelude API — frequently asked questions

Does Prelude have an API?

Yes. APIs.io lists 4 APIs from Prelude, including Prelude Lookup API, Prelude Transactional API and Prelude Verification API, and 1 more.

Is there an OpenAPI specification for the Prelude API?

Yes. APIs.io indexes 4 OpenAPI specifications for Prelude, each linked for download from this page.

How do I authenticate with the Prelude API?

Prelude uses bearer-token authentication (http · 1 scheme). The details are profiled on APIs.io as Prelude So Authentication.

How much does the Prelude API cost?

APIs.io lists 3 pricing plans for Prelude, with each plan's price, limits and inclusions under Pricing Plans on this page.

Is the Prelude API ready for AI agents?

Prelude has a Kin Score of 26.1 out of 100 (emerging) and an Agent Readiness score of 19.6 (agent-aware), scored by API Evangelist on 2026-10-31.

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