sinch-authentication

A setup and troubleshooting guide for authenticating with Sinch APIs, including Conversation, Voice, Verification, Numbers, Fax, and Mailgun.

In plain words
What is it for?
Configure OAuth2, Basic authentication, application signing, or API keys for a Sinch product and troubleshoot failed authentication.
Why use it?
It helps identify the right credentials and resolve access errors such as unauthorized or invalid-signature responses.

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

Made for: Claude Code, Codex.

Per session 87 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,213 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 $0.00087 $0.02213
Opus 5 $0.00044 $0.01107
Sonnet 5 $0.00017 $0.00443
Haiku 4.5 $0.00009 $0.00221

Measured yesterday against content hash d1515db10e96, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

sinch-authentication 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 yesterday.

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.

Cross-cutting skill that covers credential setup and authentication for all Sinch APIs. Determines the correct auth model, provides curl examples, SDK init code, and troubleshooting for common auth errors.
Origin

This is a copy

100% identical to sinch-authentication — 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/authentication/SKILL.md · 182 lines

How it starts

The opening of the file, as written. The whole thing — 182 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sinch Authentication

Cross-cutting skill that covers credential setup and authentication for all Sinch APIs. Determines the correct auth model, provides curl examples, SDK init code, and troubleshooting for common auth errors.

Agent Instructions

If the user hasn't specified which Sinch product they're integrating, ask first — the auth model depends on the product. Use the decision table in Step 1 to route to the correct credentials.

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.

Quick rule: writing code → load the doc. Never cite an exact field, header, enum, or encoding you only saw in a summary.

Step 1: Identify the Auth Model

Determine which model applies based on the Sinch product:

Read the full file on GitHub · 182 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. yesterday First seen · 182 lines · 87 tokens per session scan A d1515db10e96

Subscribe to this mod's changes

sinch-authentication is a skill published in the GitHub repository sinch/sinch-plugins (6 stars, last pushed 19d ago), licensed Apache-2.0. It adds 87 tokens to every session and 2,213 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to sinch-authentication, differing in 0 lines, and is treated as a copy.

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