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.
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.
npx agentmods add skills/vercel-labs/emulate/twilionpx skills add vercel-labs/emulate --skill twiliogit clone --depth 1 https://github.com/vercel-labs/emulateWrote 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.
[](https://agentmods.dev/skills/vercel-labs/emulate/twilio)<a href="https://agentmods.dev/skills/vercel-labs/emulate/twilio"><img src="https://agentmods.dev/badge/skills/vercel-labs/emulate/twilio.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00056 | $0.00921 |
| Opus 5 | $0.00028 | $0.00461 |
| Sonnet 5 | $0.00011 | $0.00184 |
| Haiku 4.5 | $0.00006 | $0.00092 |
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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 74 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
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 messageGET /2010-04-01/Accounts/{AccountSid}/Messages.json- list messagesPOST /2010-04-01/Accounts/{AccountSid}/Calls.json- create outbound callPOST /verify/v2/Services/{ServiceSid}/Verifications- start verificationPOST /verify/v2/Services/{ServiceSid}/VerificationCheck- check verification codePOST /conversations/v1/Services/{ServiceSid}/Conversations- create ConversationPOST /conversations/v1/Services/{ServiceSid}/Conversations/{ConversationSid}/Participants- add participantPOST /conversations/v1/Services/{ServiceSid}/Conversations/{ConversationSid}/Messages- add messagePOST /_twilio/simulate/inbound-message- simulate inbound SMSPOST /_twilio/simulate/message-status- simulate message status callbackPOST /_twilio/simulate/inbound-call- simulate inbound call
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.
- 5d ago First seen · 74 lines · 56 tokens per session scan A 45b3f938ccd4
twilio is a skill published in the GitHub repository vercel-labs/emulate (1,629 stars, last pushed yesterday), licensed Apache-2.0. It adds 56 tokens to every session and 921 once invoked, about $0.0003 per session on Opus 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.
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