A local imitation of Twilio, a service used for text messages, phone calls, verification codes, and related webhooks. It provides REST endpoints and SDK-compatible responses without contacting Twilio.

Use it to test SMS, verification, voice, conversations, phone numbers, webhooks, status callbacks, and Twilio SDK integrations locally.

It lets you develop and test phone and messaging integrations without sending real messages, making real calls, or depending on Twilio accounts.

twilio — Skill for Claude Code by vercel-labs/emulate

About the project

emulate provides local, stateful replacements for APIs and services so software can run in CI or environments without network access. It is used by developers who need production-like integrations with services such as GitHub, Stripe, AWS, Slack, and databases during testing. Its catalogue skills and instruction support agent workflows that use these local emulators.

vercel-labs/emulate · 1,947 stars · on GitHub · emulate.dev

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.

Any agent

npx skills add vercel-labs/emulate --skill twilio

Clone the repo

git clone --depth 1 https://github.com/vercel-labs/emulate

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/vercel-labs/emulate/twilio/github.svg)](https://agentmods.dev/skills/vercel-labs/emulate/twilio)

Your own site

<a href="https://agentmods.dev/skills/vercel-labs/emulate/twilio"><img src="https://agentmods.dev/badge/skills/vercel-labs/emulate/twilio/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/vercel-labs/emulate/twilio"><img src="https://agentmods.dev/badge/skills/vercel-labs/emulate/twilio.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,135 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 3 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

medium MCP Rug Pull · line 4
npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.

Fix: Pin the version: npx @scope/[email protected]
medium MCP Rug Pull · line 14
npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.

Fix: Pin the version: npx @scope/[email protected]
medium Data Exfiltration · line 34
Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.

How audits are shown

Origin original No closer match found 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.

Model	Per session	Once invoked
Fable 5.1	$0.00056	$0.01135
Opus 5.5	$0.00022	$0.00454
Sonnet 5.5	$0.00011	$0.00227
Haiku 4.5	$0.00006	$0.00113

Measured 21d ago against content hash d2b0b9617cb6, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

twilio scanned grade A with 0 findings 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 21d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/twilio/SKILL.md · 80 lines

How it starts

The opening of the file, as written. The whole thing — 80 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Twilio API Emulator

Stateful Twilio REST emulation with seeded accounts, Auth Tokens, API keys, incoming phone numbers, Programmable Messaging, Messaging Services, Verify, basic Voice calls, Conversations REST resources, signed webhooks, local simulator routes, and an inspector.

Start

Local listeners bind to 127.0.0.1 by default. For access from containers or other machines, pass --host 0.0.0.0 to the CLI or hostname: '0.0.0.0' to createEmulator. Configure --base-url or baseUrl for advertised URLs reachable by those clients.

npx emulate --service twilio

Default URL: http://localhost:4013 when all services are started, or http://localhost:4000 when Twilio is the only service.

Defaults

TWILIO_ACCOUNT_SID=AC00000000000000000000000000000000
TWILIO_AUTH_TOKEN=twilio_test_auth_token
TWILIO_API_KEY=SK00000000000000000000000000000000
TWILIO_API_SECRET=twilio_test_api_secret
TWILIO_PHONE_NUMBER=+15551234567
TWILIO_VERIFY_SERVICE_SID=VA00000000000000000000000000000000

URL Mapping

Real Twilio URL	Emulator URL
`https://api.twilio.com/2010-04-01/...`	`$TWILIO_EMULATOR_URL/2010-04-01/...`
`https://messaging.twilio.com/v1/...`	`$TWILIO_EMULATOR_URL/messaging/v1/...`
`https://verify.twilio.com/v2/...`	`$TWILIO_EMULATOR_URL/verify/v2/...`

The official Node SDK builds absolute Twilio product URLs. In SDK tests, use a custom request client that rewrites those hosts to the emulator prefixes above.

Auth

HTTP Basic auth accepts either:

Account SID and Auth Token
API Key SID and API Key Secret

Core Routes

POST /2010-04-01/Accounts/{AccountSid}/Messages.json - create outbound message
GET /2010-04-01/Accounts/{AccountSid}/Messages.json - list messages
POST /2010-04-01/Accounts/{AccountSid}/Calls.json - create outbound call
POST /verify/v2/Services/{ServiceSid}/Verifications - start verification
POST /verify/v2/Services/{ServiceSid}/VerificationCheck - check verification code
POST /conversations/v1/Services/{ServiceSid}/Conversations - create Conversation
POST /conversations/v1/Services/{ServiceSid}/Conversations/{ConversationSid}/Participants - add participant
POST /conversations/v1/Services/{ServiceSid}/Conversations/{ConversationSid}/Messages - add message
POST /_twilio/simulate/inbound-message - simulate inbound SMS
POST /_twilio/simulate/message-status - simulate message status callback
POST /_twilio/simulate/inbound-call - simulate inbound call

Read the full file on GitHub · 80 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.

21d ago Changed · +2 lines d2b0b9617cb6
29d ago Changed · +4 lines bf04caab20f4
1mo ago First seen · 74 lines · 56 tokens per session scan A 45b3f938ccd4

Subscribe to this mod's changes

twilio is a skill published in the GitHub repository vercel-labs/emulate (1,947 stars, last pushed 2d ago), licensed Apache-2.0. It adds 56 tokens to every session and 1,135 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Backend and APIs Testing

server-side-calls

Call tRPC procedures directly from server code using t.createCallerFactory() and router.createCaller(context) for integration testing, internal server logic, and custom API endpoints. Catch TRPCError and extract HTTP status with getHTTPStatusCodeFromError(). Error handling via onError option.

trpc/trpc · 61 tokens

mem0-test-integration

Verify a Mem0 integration produced by /mem0-integrate. Runs in the same workspace on the same branch (loose coupling) — installs dependencies, runs the repo's native test suite, then exercises a real end-to-end smoke flow against the user's API key. Produces a scorecard. TRIGGER when: user has just run /mem0-integrate…

mem0ai/mem0 · 207 tokens

prowler-test-api

Testing patterns for Prowler API: JSON:API, Celery tasks, RLS isolation, RBAC. Trigger: When writing tests for api/ (JSON:API requests/assertions, cross-tenant isolation, RBAC, Celery tasks, viewsets/serializers).

prowler-cloud/prowler · 62 tokens

python-sdk

Implement or modify Python SDK behavior under python/composio, including tools, toolkits, sessions, auth configs, connected accounts, client integration, and shared Python models. Use for Python core runtime/API work; pair with python-testing and cross-sdk-parity when TypeScript must match.

ComposioHQ/composio · 60 tokens

convex-test

Generate convex-test tests for the app's Convex functions.

openclaw/clawhub · 16 tokens

voiden

Create and edit Voiden .void files for API testing. Covers the .void file format and all enabled extension block types.

VoidenHQ/voiden · 28 tokens