AgentSIM MCP server

agentsim-mcp

Availability: Live SMS is self-serve for owned public HTTPS services after exact-origin verification and an allow policy. Hobby includes 10 live US SMS sessions per UTC month, with one active live session per account and no card required. Builder is $99/month and includes 50 live US SMS sessions. Checkout shows tax and renewal terms before payment, and existing agreements keep their terms. Check current access and channel support before using live examples.

MCP server that exposes AgentSIM challenge tools to AI coding assistants: Codex CLI, Claude Code, Cursor, Windsurf, and any other MCP-compatible host. Primary tools: open_challenge, wait_for_verdict. Aliases: provision_number, wait_for_otp.

Setup

For Codex CLI, follow Connect Codex. It covers key handling, the SMS wait timeout, and browser access. Then use the complete phone sign-in prompt.

Claude Code

claude mcp add agentsim -e AGENTSIM_API_KEY=asm_live_xxx -- uvx agentsim-mcp

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "agentsim": {
      "command": "uvx",
      "args": ["agentsim-mcp"],
      "env": {
        "AGENTSIM_API_KEY": "asm_live_xxx"
      }
    }
  }
}

Cursor / Windsurf

Add agentsim-mcp as a stdio MCP server with AGENTSIM_API_KEY in the environment config.

Remote (no install)

Connect directly to the hosted MCP server without installing anything locally:

{
  "mcpServers": {
    "agentsim": {
      "type": "streamable-http",
      "url": "https://mcp.agentsim.dev/mcp",
      "headers": {
        "x-api-key": "asm_live_..."
      }
    }
  }
}

The hosted endpoint uses stateless HTTP and does not issue mcp-session-id headers. The session_id returned by AgentSIM tools identifies a challenge and remains valid across tool calls.

Tools

Control-Plane Nouns (Recommended)

Tool	Description
identify_agent	Add a stable agent ID to the console without opening a challenge, sending SMS, or using allowance
open_challenge	Open an authentication challenge session for a required owned service_url; accepts channel (sms_otp | email_otp | magic_link | webauthn_required), returns session ID + identifier
wait_for_verdict	Long-poll for the challenge verdict — returns structured outcome including otp_code, magic_link, or webauthn_required; policy denial fails on open
get_messages	Read SMS metadata and parsed codes; reading codes consumes them
release_number	Release a session early (allocation returned to pool)
list_numbers	List all active sessions for this account

Legacy Aliases (Backward Compatibility)

Tool	Maps to	Description
provision_number	open_challenge(channel=sms_otp)	Provision a temporary programmable US number for SMS OTP — kept for backward compatibility
wait_for_otp	wait_for_verdict	Legacy wait with automatic extension after timeout by default; number may be unchanged

Auth

For stdio, set AGENTSIM_API_KEY in the process environment. For hosted HTTP, every request must send its own x-api-key; the server validates and forwards that caller-scoped key. Get a key at console.agentsim.dev.

Supported Countries

US