OpenAI Codex is a coding agent that runs in your terminal with MCP support. By connecting AgentCall's MCP server, you can give Codex the ability to provision phone numbers, send SMS, extract OTP verification codes, configure inbound AI receptionists, and place outbound AI voice calls, all without leaving your development environment.

This guide shows you how to set it up in under 2 minutes.

What You Need

OpenAI Codex. Install via CLI (npm install -g @openai/codex) or search "Codex" in the VS Code Extensions Marketplace and install the official OpenAI extension directly.
An AgentCall API key (free at agentcall.co/sign-up).

Step 1: Get Your AgentCall API Key

New accounts receive a one-time 72-hour live trial with one US/Canada local number, 300 managed inbound AI seconds (five minutes) total, and five SMS send attempts to verified destinations. Card verification is required before number allocation; the clock starts when allocation succeeds. There is no monthly reset or automatic paid subscription. Live OTP extraction and outbound calls require Pro. Existing Free accounts retain their assigned monthly allowances. Read the account's offerVersion, trial and limits rather than assuming every Free account has the same offer. Only describe a monthly reset when the account response supplies a non-null resetsAt.

Step 2: Configure AgentCall MCP in Codex

Codex reads MCP server configuration from ~/.codex/config.toml (TOML, not JSON). The recommended path is the hosted endpoint, which Codex supports as a streamable HTTP server. Export your key as an environment variable, then add this block:

export AGENTCALL_API_KEY=ac_live_your_key_here

# ~/.codex/config.toml
[mcp_servers.agentcall]
url = "https://api.agentcall.co/mcp"
bearer_token_env_var = "AGENTCALL_API_KEY"

Save the file and restart Codex. It connects to the hosted server and auto-discovers all 62 AgentCall tools. Prefer to run the server locally? Use the npm package over stdio instead:

[mcp_servers.agentcall]
command = "npx"
args = ["-y", "@agentcall/mcp-server"]

[mcp_servers.agentcall.env]
AGENTCALL_API_KEY = "ac_live_your_key_here"

Step 3: Verify the Connection

Launch Codex and ask it about phone tools:

You: What phone tools do you have access to?

Codex: I have 62 AgentCall tools available:
- provision_number. Provision a new phone number.
- send_sms. Send an SMS message.
- wait_for_otp. Long-poll for OTP verification codes.
- initiate_ai_call. Start an AI voice conversation.
- configure_inbound_ai. Set up an inbound AI receptionist.
... and more

Step 4: Use Phone Tools in Your Workflow

Here are practical examples of what Codex can do with AgentCall:

Automated QA Testing

Live OTP extraction requires Pro.

You: I need to test the signup flow on my staging app. Provision a number,
     enter it in the form at staging.myapp.com, and verify the OTP.

Codex: I'll handle the full flow:
1. [Calls provision_number] Got +1 (312) 555-0198
2. [Enters number in signup form]
3. [Calls wait_for_otp, polling for SMS]
4. OTP received: 592741
5. [Enters code in verification field]
Signup verified successfully.

Send Notifications

New trials include five texts to verified destinations in total. Plan on Pro for anything beyond testing.

You: Send an SMS to +12125559876 saying "Deployment completed successfully"

Codex: [Calls send_sms]
Message sent from +1 (312) 555-0198.

AI Voice Calls

Outbound AI calls require Pro.

You: Call +12125559876 and schedule a meeting for next Tuesday at 2pm

Codex: [Calls initiate_ai_call with scheduling prompt]
Call completed. Meeting confirmed for Tuesday at 2:00 PM.
Full transcript available.

Alternative: Via Smithery

AgentCall is listed on Smithery, a public MCP server registry. Install via the Smithery CLI, which writes the right config for your client:

npm install -g smithery
smithery mcp add agentcall/agentcall \
  --headers '{"agentcallApiKey":"ac_live_your_key_here"}'

Smithery also hosts its own MCP URL for the server at https://agentcall--agentcall1.run.tools. You do not need it for Codex, since the hosted endpoint above works directly.

Which Transport Should I Pick?

AgentCall's native hosted MCP endpoint is https://api.agentcall.co/mcp, with Authorization: Bearer ac_live_.... It works in Codex, Claude Desktop, Claude Code, Cursor, and Windsurf, and always serves the current tool list. Use the stdio npm package if you want the server to run locally; update it with @latest to pick up new tools.

All 62 Tools

Once connected, Codex has access to the full AgentCall toolkit, plus five built-in MCP prompts (setup-agent-phone, send-and-track-sms, ai-outbound-call, follow-up-on-call, setup-inbound-ai-receptionist):

Phone Numbers (7): provision_number, list_numbers, get_number, release_number, update_number_label, update_number_voice, update_number_language
Inbound AI Voice (2): configure_inbound_ai, disable_inbound_ai
Premium Voice (3): list_premium_voices, set_premium_voice, disable_premium_voice
Voice Billing (2): set_byok_openai_key, disable_byok
Outbound AI Defaults (3): set_outbound_defaults, get_outbound_defaults, clear_outbound_defaults
SMS (7): send_sms, get_inbox, get_message, wait_for_otp, list_sms_conversations, get_sms_conversation, reply_to_sms_conversation
Voice Calls and Speech (7): initiate_call, initiate_ai_call, get_call, hangup_call, get_call_transcript, list_calls, synthesize_speech
Scheduling (3): create_schedule, list_schedules, cancel_schedule
Webhooks (4): create_webhook, list_webhooks, rotate_webhook_secret, delete_webhook
Usage (1): get_usage
AgentFM (1): request_agentfm_callback (AI host calls a number back to record a short podcast, no account required)
Call Memory, Read (10): list_contacts, get_contact, get_contact_by_phone, get_next_call_context, get_current_memory, get_memory, get_memory_timeline, list_memory_candidates, list_call_reports, get_call_report
Call Memory, Write and Briefs (10): update_contact, purge_contact, update_memory, delete_memory, approve_memory_candidate, reject_memory_candidate, set_memory_enabled, list_briefs, acknowledge_brief, resolve_brief
Account and Upgrade (2): get_plan, upgrade_to_pro

AgentCall + Codex Use Cases

Automated end-to-end testing of SMS verification flows in CI/CD
AI-powered outbound calling for sales, scheduling, and surveys
Inbound AI receptionist setup driven from your terminal
Real-time SMS notifications from your development pipeline
Phone number provisioning for multi-tenant SaaS apps
OTP extraction for automated account creation in testing

Pricing

New accounts receive a one-time 72-hour live trial with one US/Canada local number, 300 managed inbound AI seconds (five minutes) total, and five SMS send attempts to verified destinations. Card verification is required before number allocation; the clock starts when allocation succeeds. There is no monthly reset or automatic paid subscription. Live OTP extraction and outbound calls require Pro. Existing Free accounts retain their assigned monthly allowances. Read the account's offerVersion, trial and limits rather than assuming every Free account has the same offer. Only describe a monthly reset when the account response supplies a non-null resetsAt.
Pro is $19.99/month plus number rental and usage: local/mobile numbers $2/month each, toll-free $2.50/month, outbound SMS $0.015/message, standard outbound voice $0.035/min, managed AI voice $0.40/min, BYOK voice $0.10/min plus your AI provider's charges, or Premium Voice $0.59/min. AI calls round up to whole minutes per call. New-account destination/business verification can still apply after upgrading. Call recording is $0.01/min. There are 10 managed AI voices, including the natural-sounding marin and cedar. Post-call email summaries are included on any plan with inbound AI configured.

Next Steps

Questions? Email support@agentcall.co.

How to Use AgentCall MCP Server with OpenAI Codex in VS Code