Connect
Optimize
Secure
JustCall MCP Server
for AI Agents
Production-ready JustCall MCP server with 73 extensible actions — plus built-in authentication, security, and optimized execution.
JustCall MCP Server
Built by 
StackOne
StackOne 
Coverage
73 Agent Actions
Create, read, update, and delete across JustCall — and extend your agent's capabilities with custom actions.
Authentication
Agent Tool Authentication
Per-user OAuth in one call. Your JustCall MCP server gets session-scoped tokens with zero credentials stored on your infra.
Agent Auth →
Security
Agent Protection
Every JustCall tool response scanned for prompt injection in milliseconds — 88.7% accuracy, all running on CPU.
Prompt Injection Defense →
Performance
Max Agent Context. Min Cost.
Free up to 96% of your agent's context window to enhance reasoning and reduce cost, on every JustCall call.
Tools Discovery →What is the JustCall MCP Server?
A JustCall MCP server lets AI agents read and write JustCall data through the Model Context Protocol — Anthropic's open standard for connecting LLMs to external tools. StackOne's JustCall MCP server ships with 73 pre-built actions, fully extensible via the Connector Builder — plus managed authentication, prompt injection defense, and optimized agent context. Connect it from MCP clients like Claude Desktop, Cursor, and VS Code, or from agent frameworks like OpenAI Agents SDK, LangChain, and Vercel AI SDK.
All JustCall MCP Tools and Actions
Every action from JustCall's API, ready for your agent. Create, read, update, and delete — scoped to exactly what you need.
Calls
- List Calls
Retrieve a paginated list of all calls with optional filtering by date, agent, direction, type, and more.
- Get Call
Retrieve details of a specific call by its ID.
- Update Call
Update notes or rating for a specific call.
Texts
- List Texts
Retrieve a paginated list of all SMS and MMS messages.
- Get Text
Retrieve details of a specific text message by ID.
Tags
- Create Tag
Create a new tag for SMS categorization.
- List Tags
Retrieve all SMS tags in the account.
- Get Tag
Retrieve details of a specific SMS tag.
- Delete Tag
Delete an SMS tag by ID.
Threads
- List Threads
Retrieve all SMS conversation threads.
- Get Thread
Retrieve a specific SMS conversation thread with its messages.
Messages
- Send Message
Send a text, template, or media WhatsApp message.
- List Messages
Retrieve a paginated list of all WhatsApp messages.
- Get Message
Retrieve details of a specific WhatsApp message by ID.
Contacts
- Create Contact
Create a new contact with name, phone, email, and other details.
- List Contacts
Retrieve a paginated list of all contacts with optional filtering.
- Get Contact
Retrieve details of a specific contact by ID.
- Update Contact
Update an existing contact's information.
- Delete Contact
Delete a contact by ID or phone number.
Phone Numbers
- List Phone Numbers
Retrieve a paginated list of all phone numbers in the account.
- Get Phone Number
Retrieve details of a specific phone number by ID.
Users
- List Users
Retrieve a paginated list of all agents/users in the account.
- Get User
Retrieve details of a specific user/agent by ID.
User Groups
- List User Groups
Retrieve all user groups (teams) in the account.
- Get User Group
Retrieve details of a specific user group by ID.
Sales Dialer Calls
- List Sales Dialer Calls
Retrieve a paginated list of all Sales Dialer calls.
- Get Sales Dialer Call
Retrieve details of a specific Sales Dialer call by ID.
Campaigns
- Create Campaign
Create a new Sales Dialer campaign.
- List Campaigns
Retrieve all Sales Dialer campaigns.
- Get Campaign
Retrieve details of a specific Sales Dialer campaign.
- Update Campaign
Update an existing Sales Dialer campaign.
Sales Dialer Contacts
- Create Sales Dialer Contact
Create a new Sales Dialer contact.
- List Sales Dialer Contacts
Retrieve all Sales Dialer contacts.
- Get Sales Dialer Contact
Retrieve details of a specific Sales Dialer contact.
- Update Sales Dialer Contact
Update an existing Sales Dialer contact.
- Delete Sales Dialer Contact
Delete a Sales Dialer contact by ID.
Appointments
- Create Appointment
Create a new appointment in the calendar.
- Get Appointment
Retrieve details of a specific appointment by ID.
Other (35)
- Send SMS/MMS
Send an SMS or MMS message to a phone number.
- Add Tag To Thread
Add a tag to a JustCall number and contact conversation thread.
- Add Contact To Campaign
Add a contact to a Sales Dialer campaign.
- Add URL To Webhook
Subscribe a URL to receive webhook events.
- Get Call Journey
Retrieve the sequential journey stages showing how a call was routed.
- Get Call Voice Agent Data
Retrieve AI Voice Agent insights and actions executed during a call.
- Download Call Recording
Download the MP3 recording file for a completed call.
- Get Account Analytics
Retrieve account-level call analytics including SLA, connect rate, and durations.
- Get Agent Analytics
Retrieve per-agent call performance metrics.
- Get Number Analytics
Retrieve per-phone-number call metrics.
- List Templates
Retrieve all approved WhatsApp message templates.
- List Blacklisted Contacts
Retrieve all contacts on the blacklist, DND, or DNM lists.
- List Voice Agents
Retrieve all configured AI Voice Agents.
- List Campaign Contacts
Retrieve all contacts in a specific campaign.
- Get Bulk Import Status
Check the progress of a bulk contact import.
- List Sales Dialer Contact Custom Fields
Retrieve the custom field schema for Sales Dialer contacts.
- Get Sales Dialer Agent Analytics
Retrieve agent and campaign performance metrics for Sales Dialer.
- List Calls AI Data
Retrieve AI analysis data for calls including sentiment, scores, and summaries.
- Get Call AI Data
Retrieve AI analysis data for a specific call.
- List Meetings AI Data
Retrieve AI analysis data for meetings.
- Get Meeting AI Data
Retrieve AI analysis data for a specific meeting.
- List Available Slots
Retrieve available scheduling slots for appointments.
- List Subscribed Webhooks
Retrieve all subscribed webhook events.
- Update Contact Status
Add or remove a contact from blacklist, DND, or DNM lists.
- Update User Availability
Update an agent's availability status for call routing.
- Remove Tag From Thread
Remove a tag from a conversation thread.
- Remove Contact From Campaign
Remove a contact from a Sales Dialer campaign.
- Remove URL From Webhook
Remove a URL from a webhook subscription.
- Check Reply
Check the most recent inbound SMS reply from a contact.
- Check Message Reply
Check if a WhatsApp reply has been received from a contact.
- Bulk Add Contacts To Blacklist
Bulk add contacts to DND, DNM, or blacklist.
- Detect Incoming Number
Detect phone number type (Mobile, Landline, VOIP) and carrier.
- Initiate Call
Trigger an outbound call from an AI Voice Agent.
- Bulk Import Sales Dialer Contacts
Bulk import contacts to the Sales Dialer.
- Bulk Add Contacts To DNCA
Bulk add contacts to the Do Not Call Again list.
Set Up Your JustCall MCP Server in Minutes
One endpoint. Any framework. Your agent is talking to JustCall in under 10 lines of code.
MCP Clients
Agent Frameworks
JSON{
"mcpServers": {
"stackone": {
"command": "npx",
"args": [
"-y",
"mcp-remote@latest",
"https://api.stackone.com/mcp?x-account-id=<account_id>",
"--header",
"Authorization: Basic <YOUR_BASE64_TOKEN>"
]
}
}
}JustCall MCP Server Resources
MCP Code Mode: Keeping Tool Responses Out of Agent Context
Anthropic's code_execution processes data already in context. Custom MCP code mode keeps raw tool responses in a sandbox. 14K tokens vs 500.
11 min
Comparing BM25, TF-IDF, and Hybrid Search for MCP Tool Discovery
Benchmarking BM25, TF-IDF, and hybrid search for MCP tool discovery across 916 tools. The 80/20 TF-IDF/BM25 hybrid hits 21% Top-1 accuracy in under 1ms.
10 min
Indirect Prompt Injection Defense for MCP Tools: A Technical Guide
MCP tools that read emails, CRM records, and tickets are indirect prompt injection vectors. Here's how we built a two-tier defense that scans tool results in ~11ms.
12 min
JustCall MCP Server FAQ
JustCall MCP server vs direct API integration — what's the difference?
A JustCall MCP server and direct API integration serve different use cases. Direct API integration is for software-to-software — backend code calling JustCall. A JustCall MCP server is for AI agents — MCP clients like Claude and Cursor, plus framework agents built with OpenAI, LangChain, or Vercel AI — discovering and calling JustCall at runtime. StackOne provides both.
How does JustCall authentication work for AI agents?
JustCall authentication for AI agents works through a StackOne Connect Session. Create one via the dashboard or the SDK — you get an auth link and ready-to-paste config for Claude Desktop, Cursor, and other MCP clients. Your user authenticates their own JustCall account; StackOne handles token exchange, storage, and refresh. Credentials never reach the LLM, and each user is isolated via
origin_owner_id.Are JustCall MCP tools vulnerable to prompt injection?
Yes — JustCall MCP tools can be vulnerable to indirect prompt injection. Any tool that reads user-written content — documents, messages, tickets, records, or free-text fields — is a potential vector. StackOne Defender scans every tool response before it enters the agent's context — regex patterns in ~1ms, then a MiniLM classifier in ~4ms. 88.7% accuracy, CPU-only.
What is the context bloat of a JustCall agent and how do I avoid it?
Context bloat happens when JustCall tool schemas and API responses eat your JustCall agent's memory, preventing it from reasoning effectively. A single JustCall query can return a massive JSON response, and connecting multiple tools compounds the problem. Tools Discovery and Code Mode reduce context bloat — loading only relevant tools per query and keeping raw responses out of the agent's context.
Can I limit which actions my JustCall agent can access?
Yes — you can limit which actions your JustCall agent can access directly from the StackOne dashboard. Toggle actions on or off, or restrict them to specific accounts, with no code changes to your agent. Session tokens can be scoped to exact actions so if one leaks, exposure stays contained.
Can I create custom agent actions for my JustCall MCP server?
Yes — you can create custom agent actions for your JustCall MCP server using Connector Builder. It's an integration agent your coding assistant (Claude Code, Cursor, or Copilot) can invoke to research JustCall's API, generate production-ready connector YAML, test against the live API, and validate before you ship.
When should I NOT use a JustCall MCP server?
Skip a JustCall MCP server if your integration is purely software-to-software — direct JustCall API integration is simpler when no AI agent is involved. For deterministic, compliance-critical operations (financial transactions, regulatory reporting), direct API gives you predictable behavior without agent-driven decision-making. MCP shines when AI agents need to dynamically discover and call JustCall actions at runtime.
What AI frameworks and AI clients does the StackOne JustCall MCP server support?
The StackOne JustCall MCP server supports both. MCP clients (paste-and-go apps): Claude Desktop, Claude Code, Cursor, VS Code, Goose. Agent frameworks (code SDKs you build with): OpenAI Agents SDK, Anthropic, Vercel AI, Google ADK, CrewAI, Pydantic AI, LangChain, LangGraph, Azure AI Foundry.
Put your AI agents to work
All the tools you need to build and scale AI agent integrations, with best-in-class connectivity, execution, and security.