MCP server - Larynth

Larynth hosts a Model Context Protocol (MCP) server for your workspace. An AI assistant or agent framework that speaks MCP can use it to read your calls, agents, contacts, numbers, campaigns and balance, and to take a few actions such as pausing an agent or placing a call. Each tool runs the matching API operation with your API key. The server can do nothing the key can’t: the same scopes, compliance checks, balance checks and rate limits apply.

Server URL

Use the MCP URL of your workspace’s region. You find it in the dashboard under Developers, on the Docs tab.

Region	URL
United States	`https://api-us.larynth.com/mcp`

The server uses the Streamable HTTP transport and answers with JSON. It supports MCP protocol versions 2025-11-25, 2025-06-18 and 2025-03-26.

Connect

Create an API key in the dashboard with only the scopes the assistant needs, and send it as a bearer token. Dashboard logins and session cookies are not accepted. Most MCP clients take a configuration like this. Field names vary between clients, so check yours.

{
  "mcpServers": {
    "larynth": {
      "type": "http",
      "url": "https://api-us.larynth.com/mcp",
      "headers": {
        "Authorization": "Bearer ${LARYNTH_API_KEY}"
      }
    }
  }
}

Keep the key in an environment variable or your client’s secret store. Never paste it into a shared file or a prompt. To check the connection by hand, start a session and list the tools your key can use:

curl -i https://api-us.larynth.com/mcp \
  -H "Authorization: Bearer $LARYNTH_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"curl","version":"1"}}}'

The response carries an Mcp-Session-Id header. Send it with every later request:

curl https://api-us.larynth.com/mcp \
  -H "Authorization: Bearer $LARYNTH_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "Mcp-Session-Id: $SESSION_ID" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/list"}'

Tools

tools/list returns only the tools your key’s scopes allow. A key with calls:read alone sees the three call-reading tools and nothing else.

Tool	What it does	Scope
`list_calls`	List calls with filters, newest first	`calls:read`
`get_call`	Get one call	`calls:read`
`get_call_analysis`	Get a call’s summary and extracted data	`calls:read`
`create_call`	Place one outbound call	`calls:write`
`list_agents`	List agents	`assistants:read`
`get_agent`	Get one agent	`assistants:read`
`pause_agent`	Stop an agent answering new calls	`assistants:write`
`resume_agent`	Let a paused agent answer again	`assistants:write`
`list_contacts`	List contacts	`contacts:read`
`get_contact`	Get one contact	`contacts:read`
`create_contact`	Create a contact	`contacts:write`
`list_numbers`	List phone numbers	`numbers:read`
`get_number`	Get one phone number	`numbers:read`
`list_campaigns`	List campaigns	`campaigns:read`
`get_campaign`	Get one campaign	`campaigns:read`
`pause_campaign`	Pause a campaign’s dialing	`campaigns:write`
`get_balance`	Prepaid balance	`billing:read`
`get_usage`	Spend by category, agent, day or number	`billing:read`
`get_spend_limits`	Daily cap and monthly budget with today’s and this month’s spend	`billing:read`

Each tool’s input schema mirrors the parameters and body of its API operation, so the API reference describes every field. The result is the operation’s JSON response. There are no tools for API keys, webhooks, top-ups, bundles or team members. Those stay in the dashboard. The server offers tools only: no resources, prompts or sampling.

Placing calls

create_call needs the calls:write scope. It goes through every check an API call goes through: compliance rules, calling windows, caller ID, consent, your balance and your spend limits. A call that fails a check is not placed, and the tool returns the reason. Use only numbers you have the right to call. See outbound calls with consent.

Idempotency

Tools that change something accept an optional idempotency_key argument. It works like the Idempotency-Key header: repeating a tool call with the same key within 24 hours returns the first result instead of acting twice. Without one, the server derives a key from your API key, the MCP session and the JSON-RPC request id. A message that is delivered twice is then applied once. A new request id is a new action.

Results and errors

A result larger than 256 KB is not returned. The tool reports an error instead; ask again with filters or a smaller limit. When the API refuses a tool call, the tool result is marked as an error and holds the same problem JSON the API returns, with its code. For example, a key without the needed scope gets auth.scope_missing. The server itself refuses a request before any tool runs in these cases:

Status	Code	Meaning
`401`	`auth.unauthenticated`	The `Authorization` header is missing or malformed, the key is unknown, expired or revoked, or the request used a session cookie.
`403`	`workspace.test_restricted`	The workspace is a test workspace. The MCP server is not available there.
`429`	`rate_limited`	Too many requests. The same limits as the API apply.

A request after initialize without an Mcp-Session-Id header gets 400.

​Server URL

​Connect

​Tools

​Placing calls

​Idempotency

​Results and errors