Protocol

The Rerun MCP server is a stateless JSON-RPC 2.0 endpoint. There is no SSE stream, no session id and no long-lived connection. Every request is a POST that carries its own authentication and gets a complete answer.

POST https://app.rerun.build/api/mcp/account
Authorization: Bearer rk_your_key
Content-Type: application/json

Only POST is handled. A client that opens an SSE stream first will fail, and that is expected.

initialize

Optional in practice, since the server keeps no state, but every MCP client sends it.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": { "protocolVersion": "2025-06-18" }
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "protocolVersion": "2025-06-18",
    "capabilities": { "tools": {} },
    "serverInfo": { "name": "rerun", "version": "1.0.0" }
  }
}

Supported protocol versions are 2025-06-18, 2025-03-26, 2024-11-05 and 2024-10-07. The server echoes yours when it recognises it, and answers 2025-06-18 otherwise. The only capability is tools. The server exposes no resources, no prompts and no sampling, and it never sends a notification to the client. Notifications you send to it are accepted with a 202 and an empty body.

tools/list

Returns the full tool list in one shot. There is no pagination cursor.

{ "jsonrpc": "2.0", "id": 2, "method": "tools/list" }

The list is static: all 45 tools are advertised to every key, including the 12 template authoring tools. Calling a template tool without an expert sandbox account fails at call time with a readable message. See Template tools.

tools/call

{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "tools/call",
  "params": {
    "name": "list_agents",
    "arguments": {}
  }
}

{
  "jsonrpc": "2.0",
  "id": 3,
  "result": {
    "content": [{ "type": "text", "text": "{\"agents\":[…]}" }],
    "structuredContent": { "agents": [] }
  }
}

Every result carries the same payload twice: once as JSON encoded into content[0].text for clients that only read text, and once as a real object in structuredContent. Read structuredContent if your client supports it.

Errors

Two error shapes exist, and the distinction matters.

Protocol errors

Returned for a malformed request. HTTP status is still 200.

Code	Meaning
`-32700`	The body is not valid JSON
`-32601`	Unknown method

{ "jsonrpc": "2.0", "id": null, "error": { "code": -32700, "message": "Parse error" } }

Tool errors

A tool that throws does not produce a JSON-RPC error. It produces a normal result flagged with isError, so a calling model reads the reason and corrects its arguments.

{
  "jsonrpc": "2.0",
  "id": 3,
  "result": {
    "content": [{ "type": "text", "text": "{\"error\":\"Agent not found\"}" }],
    "isError": true
  }
}

Messages are written to be actionable: a missing required argument, an agent that belongs to another workspace, a plan limit reached, a connector slug that does not exist in the catalog. If you write your own client, check result.isError on every call. A 200 response does not mean the tool succeeded.

Authentication errors

A missing or invalid key is the one case that is not JSON-RPC at all: 401 Unauthorized with a plain text body, before any parsing happens.

Destructive tools

Seven tools refuse to run unless you pass confirm: true: delete_agent, delete_skill, delete_schedule, delete_trigger, detach_connector, delete_template, remove_template_agent. Without it, the call comes back as a tool error telling you to call again once the account owner has agreed. This exists so an assistant cannot delete an agent as a side effect of a vague instruction.

Calling it with curl

Nothing about this endpoint requires an MCP client.

curl -s https://app.rerun.build/api/mcp/account \
  -H "Authorization: Bearer $RERUN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "send_message",
      "arguments": { "agentId": "…", "message": "Status report please", "waitSeconds": 60 }
    }
  }'

Get started

Tool reference

HTTP

initialize

tools/list

tools/call

Errors

Protocol errors

Tool errors

Authentication errors

Destructive tools

Calling it with curl

​initialize

​tools/list

​tools/call

​Errors

​Protocol errors

​Tool errors

​Authentication errors

​Destructive tools

​Calling it with curl

initialize

tools/list

tools/call

Errors

Protocol errors

Tool errors

Authentication errors

Destructive tools

Calling it with curl