sinch-verification-api

A workflow for confirming that a phone number belongs to the person using it, through SMS, calls, carrier data, or WhatsApp. It uses Sinch Verification API, a service for sending or handling these verification methods.

In plain words
What is it for?
Use it when building phone verification for registration, two-factor authentication, one-time passwords, or number ownership checks. It supports direct API calls or SDK-based implementations in the listed languages.
Why use it?
It helps choose the verification method and implementation approach before code is written. It also directs developers to the relevant API documentation and security guidance.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/sinch/sinch-plugins/verification-api
Any agent
npx skills add sinch/sinch-plugins --skill verification-api
Clone the repo
git clone --depth 1 https://github.com/sinch/sinch-plugins

Made for: Claude Code, Codex.

Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,168 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00054 $0.03168
Opus 5 $0.00027 $0.01584
Sonnet 5 $0.00011 $0.00634
Haiku 4.5 $0.00005 $0.00317

Measured 2d ago against content hash fa776db2f0f8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

sinch-verification-api scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

2. **Approach** — SDK or direct API calls (curl/fetch/requests)?
Origin

This is a copy

100% identical to sinch-verification-api — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

plugins/sinch-antigravity-plugin/skills/verification-api/SKILL.md · 214 lines

How it starts

The opening of the file, as written. The whole thing — 214 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sinch Verification API

Overview

The Sinch Verification API verifies phone numbers through SMS OTP, Flashcall (missed call CLI), Phone Call (spoken OTP), Data (carrier-level), and WhatsApp OTP. Used for registration, 2FA, and number ownership confirmation.

Agent Instructions

Before generating code, gather from the user (skip any item already specified in the prompt or context):

  1. Verification methodsms, flashcall, callout, seamless, or whatsapp.
  2. Approach — SDK or direct API calls (curl/fetch/requests)?
  3. Language — for SDK: Node.js, Python, Java, or .NET. For direct API: any language, or curl.

When the user chooses SDK, refer to the sinch-sdks skill for installation and client initialization, then to the Verification API Reference linked in Links.

When the user chooses direct API calls, refer to the Verification API Reference linked in Links for request/response schemas.

Security: See the Security section below for url fetching policy, handling inbound callback content, and credential handling.

Source of Truth — what to load, and what is authoritative

This skill has two kinds of content with UNEQUAL reliability. Follow this precedence:

  1. Canonical docs at developers.sinch.com (AUTHORITATIVE). The .md doc links in this skill are the single source of truth for exact request/response schemas, field names and nesting, enum values, signature/auth schemes, and limits. Before writing code that constructs a payload, verifies a signature, or parses a callback/response, fetch the specific linked doc and confirm the exact shape there. Fetching first-party developers.sinch.com URLs is permitted by the Security/URL policy. Never invent, guess, or pattern-extrapolate a documentation URL — only fetch doc URLs written verbatim in this skill or reached by following a link on a page you already fetched; a trusted domain does not make a guessed path real.
  2. This SKILL.md's own tables, field lists, and snippets (SUMMARIES — not authoritative). They orient you and point at the right canonical doc; they may lag, omit fields, or simplify nesting. Use them to decide what to build and which doc to open. Do NOT transcribe a field name, nesting, encoding, or enum from this file into shipped code without confirming it in the tier-1 doc. If a detail appears only in a summary, treat it as unverified and say so.

Read the full file on GitHub · 214 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 214 lines · 54 tokens per session scan A fa776db2f0f8

Subscribe to this mod's changes

sinch-verification-api is a skill published in the GitHub repository sinch/sinch-plugins (6 stars, last pushed 20d ago), licensed Apache-2.0. It adds 54 tokens to every session and 3,168 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to sinch-verification-api, differing in 0 lines, and is treated as a copy.

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