The authoritative catalog of every tool the MCP connector exposes through tools/call: 11 core messaging tools plus 4 agent-bridge tools. For each tool you get its arguments, defaults, JSON Schema, a ready-to-run curl request, and the response shape.

Overview

The MCP connector advertises 15 tools in its tools/list response and runs them through the single POST /mcp endpoint on the shared HTTP server (port 9090, protocol version 2025-11-25). The 11 core tools are always registered; the 4 agent-bridge tools appear only when the A2A agent registry is present.

This page is the canonical argument and schema reference. The per-tool pages under Tools carry the same operations with examples in all nine languages. For the wire-level request/response forms see Endpoints; for the failure codes see Error codes.

Tool summary

#	Tool	Category	Required args	Optional args
1	`queue_send`	Queue	`channel`, `body`	`metadata`, `tags`, `delay_seconds`, `expiration_seconds`, `max_receive_count`, `dead_letter_queue`
2	`queue_receive`	Queue	`channel`, `max_messages`	`wait_timeout_seconds`
3	`queue_peek`	Queue	`channel`, `max_messages`	(none)
4	`events_publish`	Events	`channel`, `body`	`metadata`, `tags`
5	`events_store_publish`	Events	`channel`, `body`	`metadata`, `tags`
6	`events_store_read`	Events	`channel`, `max_messages`	`from_sequence`, `from_time`
7	`events_store_read_latest`	Events	`channel`	`count`
8	`command_send`	Command / Query	`channel`, `body`	`timeout_seconds`, `metadata`, `tags`
9	`query_send`	Command / Query	`channel`, `body`	`timeout_seconds`, `metadata`, `tags`
10	`channel_list`	Channel	(none)	`type`, `pattern`
11	`channel_info`	Channel	`channel`, `type`	(none)
12	`agent_list`	Agent bridge	(none)	`skill_tags`
13	`agent_info`	Agent bridge	`agent_id`	(none)
14	`agent_send`	Agent bridge	`agent_id`, `message`	`blocking`, `context_id`, `timeout_seconds`
15	`agent_query`	Agent bridge	`agent_id`, `method`	`params`

Calling convention

Every tool is invoked the same way: a tools/call JSON-RPC request naming the tool and passing its arguments object. Only name and arguments change between tools.

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "<tool_name>",
      "arguments": { }
    }
  }'

Every successful tools/call returns a result with a content array of typed blocks — KubeMQ uses text blocks carrying the operation result as a string (often a JSON string). A tool-level failure sets isError: true in the same envelope; the JSON-RPC response itself still succeeds with HTTP 200.

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "content": [{ "type": "text", "text": "..." }],
    "isError": false
  }
}

A channel that starts with the reserved prefix _AGENTS_. is rejected — see Channel resolution. Missing required arguments return a -32602 Invalid Params JSON-RPC error, not an isError result.

Queue tools

Durable, point-to-point queue messaging. See Queue tools for language examples.

queue_send

Send a message to a queue channel.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Target queue channel. Must not start with the reserved prefix `_AGENTS_.`
`body`	string	Yes	—	Message body content
`metadata`	string	No	`""`	Optional message metadata string
`tags`	object	No	`{}`	Key-value tags for message classification
`delay_seconds`	integer	No	`0`	Delay before the message becomes visible. `0` = immediately available
`expiration_seconds`	integer	No	`0`	TTL in seconds. `0` = no expiration
`max_receive_count`	integer	No	`0`	Max receives before dead-letter. `0` = unlimited
`dead_letter_queue`	string	No	`""`	Dead-letter queue channel name

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 2,
    "method": "tools/call",
    "params": {
      "name": "queue_send",
      "arguments": {
        "channel": "example-queue",
        "body": "Hello from MCP",
        "metadata": "example-metadata",
        "tags": { "env": "dev", "source": "mcp-example" }
      }
    }
  }'

Response — a confirmation message in a single text block:

{
  "content": [{ "type": "text", "text": "Message sent successfully to queue 'example-queue'" }],
  "isError": false
}

Errors: reserved channel → isError: true; missing channel/body → -32602.

queue_receive

Receive and consume messages from a queue channel. This is a destructive read — returned messages are removed from the queue.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Source queue channel
`max_messages`	integer	Yes	`1`	Max messages to receive in a single call (1–100)
`wait_timeout_seconds`	integer	No	`5`	Long-poll wait time in seconds (1–60)

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 3,
    "method": "tools/call",
    "params": {
      "name": "queue_receive",
      "arguments": { "channel": "example-queue", "max_messages": 5 }
    }
  }'

Response — a JSON array of received messages, serialized as the text payload:

{
  "content": [{ "type": "text", "text": "[{\"body\":\"Hello from MCP\",\"metadata\":\"example-metadata\",\"tags\":{\"env\":\"dev\",\"source\":\"mcp-example\"}}]" }],
  "isError": false
}

Errors: reserved channel → isError: true; a non-existent channel returns an empty result (no error).

queue_peek

Peek at messages without consuming them — a non-destructive read; messages stay in the queue.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Source queue channel
`max_messages`	integer	Yes	`1`	Max messages to peek without consuming (1–100)

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 4,
    "method": "tools/call",
    "params": {
      "name": "queue_peek",
      "arguments": { "channel": "example-queue", "max_messages": 5 }
    }
  }'

Response — same shape as queue_receive, but the messages remain in the queue:

{
  "content": [{ "type": "text", "text": "[{\"body\":\"Hello from MCP\",\"metadata\":\"example-metadata\",\"tags\":{\"env\":\"dev\"}}]" }],
  "isError": false
}

Errors: reserved channel → isError: true; a non-existent channel returns an empty result (no error).

Events tools

Pub/sub and the persistent events store. See Events tools for language examples.

events_publish

Publish an ephemeral event (fire-and-forget; no persistence).

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Target events channel
`body`	string	Yes	—	Event body content
`metadata`	string	No	`""`	Optional event metadata string
`tags`	object	No	`{}`	Key-value tags for event classification

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 5,
    "method": "tools/call",
    "params": {
      "name": "events_publish",
      "arguments": {
        "channel": "example-events",
        "body": "Event data",
        "metadata": "event-meta",
        "tags": { "source": "mcp-example" }
      }
    }
  }'

Response:

{
  "content": [{ "type": "text", "text": "Event published successfully to channel 'example-events'" }],
  "isError": false
}

Errors: reserved channel → isError: true; missing channel/body → -32602.

events_store_publish

Publish a persistent event to the events store. Stored events receive a monotonic sequence number.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Target events-store channel
`body`	string	Yes	—	Event body content to store
`metadata`	string	No	`""`	Optional event metadata string
`tags`	object	No	`{}`	Key-value tags for event classification

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 6,
    "method": "tools/call",
    "params": {
      "name": "events_store_publish",
      "arguments": {
        "channel": "example-events-store",
        "body": "Stored event data",
        "metadata": "store-meta",
        "tags": { "source": "mcp-example" }
      }
    }
  }'

Response:

{
  "content": [{ "type": "text", "text": "Event published successfully to events store channel 'example-events-store'" }],
  "isError": false
}

Errors: reserved channel → isError: true; missing channel/body → -32602.

events_store_read

Read stored events starting from a sequence number or a timestamp.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Source events-store channel
`from_sequence`	integer	No	—	Start from this sequence number. Mutually exclusive with `from_time`
`from_time`	string	No	—	Start from this ISO 8601 timestamp. Mutually exclusive with `from_sequence`
`max_messages`	integer	Yes	—	Maximum number of messages to return (1–100)

from_sequence and from_time are mutually exclusive — supply at most one.

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 7,
    "method": "tools/call",
    "params": {
      "name": "events_store_read",
      "arguments": { "channel": "example-events-store", "from_sequence": 1, "max_messages": 10 }
    }
  }'

Response — a JSON array of stored events, each with its sequence and timestamp:

{
  "content": [{ "type": "text", "text": "[{\"body\":\"Stored event data\",\"metadata\":\"store-meta\",\"sequence\":1,\"timestamp\":\"2026-06-08T12:00:00Z\"}]" }],
  "isError": false
}

Errors: reserved channel → isError: true; a non-existent channel returns an empty result; missing channel → -32602.

events_store_read_latest

Read the N most recent stored events.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Source events-store channel
`count`	integer	No	`1`	Number of most recent events to return

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 8,
    "method": "tools/call",
    "params": {
      "name": "events_store_read_latest",
      "arguments": { "channel": "example-events-store", "count": 3 }
    }
  }'

Response — the most recent events, newest first:

{
  "content": [{ "type": "text", "text": "[{\"body\":\"Stored event 3\",\"sequence\":3},{\"body\":\"Stored event 2\",\"sequence\":2},{\"body\":\"Stored event 1\",\"sequence\":1}]" }],
  "isError": false
}

Errors: reserved channel → isError: true; a non-existent channel returns an empty result; missing channel → -32602.

Command & query tools

Synchronous request/reply. See Command & query tools for language examples.

command_send

Send a command and wait for acknowledgment from a subscriber.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Target command channel
`body`	string	Yes	—	Command body content
`timeout_seconds`	integer	No	`10`	Timeout in seconds waiting for the response
`metadata`	string	No	`""`	Optional command metadata string
`tags`	object	No	`{}`	Key-value tags for command classification

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 9,
    "method": "tools/call",
    "params": {
      "name": "command_send",
      "arguments": {
        "channel": "example-commands",
        "body": "do-work",
        "timeout_seconds": 10,
        "metadata": "cmd-meta",
        "tags": { "action": "process" }
      }
    }
  }'

Response (success):

{
  "content": [{ "type": "text", "text": "Command executed successfully on channel 'example-commands'" }],
  "isError": false
}

Errors: reserved channel, no subscriber (timeout), or subscriber rejection → isError: true; missing channel/body → -32602.

query_send

Send a query and receive a data response from a subscriber.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Target query channel
`body`	string	Yes	—	Query body content
`timeout_seconds`	integer	No	`30`	Timeout in seconds waiting for the response
`metadata`	string	No	`""`	Optional query metadata string
`tags`	object	No	`{}`	Key-value tags for query classification

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 10,
    "method": "tools/call",
    "params": {
      "name": "query_send",
      "arguments": {
        "channel": "example-queries",
        "body": "get-data",
        "timeout_seconds": 30,
        "metadata": "qry-meta",
        "tags": { "action": "lookup" }
      }
    }
  }'

Response (success) — the subscriber's reply payload as the text block:

{
  "content": [{ "type": "text", "text": "{\"data\":\"query response payload from subscriber\"}" }],
  "isError": false
}

Errors: reserved channel, no subscriber (timeout), or subscriber rejection → isError: true; missing channel/body → -32602.

Channel tools

Discovery and inspection of channels. See Channel tools for language examples.

channel_list

List channels, optionally filtered by type or name pattern. An empty list is a normal successful result.

Argument	Type	Required	Default	Description
`type`	string	No	—	Filter by channel type (`queues`, `events`, `events_store`, `commands`, `queries`)
`pattern`	string	No	—	Filter by channel name pattern or prefix

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 11,
    "method": "tools/call",
    "params": {
      "name": "channel_list",
      "arguments": {}
    }
  }'

Response — a JSON array of channel descriptors:

{
  "content": [{ "type": "text", "text": "[{\"name\":\"example-queue\",\"type\":\"queues\",\"is_active\":true},{\"name\":\"example-events\",\"type\":\"events\",\"is_active\":true}]" }],
  "isError": false
}

Errors: invalid arguments → -32602. No tool-specific failures otherwise.

channel_info

Get metadata for a specific channel.

Argument	Type	Required	Default	Description
`channel`	string	Yes	—	Channel name
`type`	string	Yes	—	Channel type (`queues`, `events`, `events_store`, `commands`, `queries`)

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 12,
    "method": "tools/call",
    "params": {
      "name": "channel_info",
      "arguments": { "channel": "example-queue", "type": "queues" }
    }
  }'

Response (success) — channel metadata with traffic counters:

{
  "content": [{ "type": "text", "text": "{\"name\":\"example-queue\",\"type\":\"queues\",\"is_active\":true,\"incoming\":5,\"outgoing\":3}" }],
  "isError": false
}

Errors: non-existent channel → isError: true.

Agent-bridge tools

These 4 tools appear in tools/list only when the A2A agent registry is present. They turn an MCP client into an A2A caller. See Agent-bridge tools for language examples and the A2A connector for the agent model.

agent_list

List registered agents, optionally filtered by skill tags. An empty list is a normal successful result.

Argument	Type	Required	Default	Description
`skill_tags`	array of string	No	—	Filter agents by skill tags

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 13,
    "method": "tools/call",
    "params": {
      "name": "agent_list",
      "arguments": {}
    }
  }'

Response — a JSON array of agents with their skills:

{
  "content": [{ "type": "text", "text": "[{\"agent_id\":\"echo-01\",\"name\":\"Echo Agent 01\",\"skills\":[{\"id\":\"echo\",\"name\":\"Echo\",\"tags\":[\"test\",\"echo\"]}]}]" }],
  "isError": false
}

Errors: invalid arguments → -32602. No tool-specific failures otherwise.

agent_info

Get detailed metadata for a specific agent.

Argument	Type	Required	Default	Description
`agent_id`	string	Yes	—	Agent identifier to look up

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 14,
    "method": "tools/call",
    "params": {
      "name": "agent_info",
      "arguments": { "agent_id": "echo-01" }
    }
  }'

Response (success) — the agent's card, including its registered HTTP url and skills:

{
  "content": [{ "type": "text", "text": "{\"agent_id\":\"echo-01\",\"name\":\"Echo Agent 01\",\"description\":\"echo agent\",\"version\":\"1.0.0\",\"url\":\"http://localhost:18080/\",\"skills\":[{\"id\":\"echo\",\"name\":\"Echo\",\"tags\":[\"test\",\"echo\"]}]}" }],
  "isError": false
}

Errors: non-existent agent → isError: true.

agent_send

Send a message to an agent. The connector builds a message/send envelope and forwards it over the broker as a Query to _AGENTS_.agents/<agent_id>.

Argument	Type	Required	Default	Description
`agent_id`	string	Yes	—	Target agent identifier
`message`	string	Yes	—	Message content to send to the agent
`blocking`	boolean	No	`true`	Wait for the agent response if `true`; fire-and-forget if `false`
`context_id`	string	No	—	Conversation context ID for multi-turn interactions
`timeout_seconds`	integer	No	—	Timeout in seconds. The server adds a +10s `GatewayTimeoutBuffer`

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 15,
    "method": "tools/call",
    "params": {
      "name": "agent_send",
      "arguments": { "agent_id": "echo-01", "message": "hello from MCP" }
    }
  }'

Response (success) — the agent's reply payload as the text block:

{
  "content": [{ "type": "text", "text": "{\"echo\":{\"method\":\"message/send\",\"params\":{\"message\":\"hello from MCP\"}},\"received_headers\":{}}" }],
  "isError": false
}

Errors: non-existent agent or timeout exceeded → isError: true.

agent_query

Query an agent with a specific JSON-RPC method.

Argument	Type	Required	Default	Description
`agent_id`	string	Yes	—	Target agent identifier
`method`	string	Yes	—	Query method to invoke (`tasks/get`, `tasks/cancel`, or a custom method)
`params`	object	No	—	Method-specific parameters

curl -X POST http://localhost:9090/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 16,
    "method": "tools/call",
    "params": {
      "name": "agent_query",
      "arguments": { "agent_id": "echo-01", "method": "tasks/get" }
    }
  }'

Response (success):

{
  "content": [{ "type": "text", "text": "{\"echo\":{\"method\":\"tasks/get\",\"params\":{}},\"received_headers\":{}}" }],
  "isError": false
}

Errors: non-existent agent or timeout exceeded → isError: true.

Tools Reference

Overview

Tool summary

Calling convention

Queue tools

queue_send

queue_receive

queue_peek

Events tools

events_publish

events_store_publish

events_store_read

events_store_read_latest

Command & query tools

command_send

query_send

Channel tools

channel_list

channel_info

Agent-bridge tools

agent_list

agent_info

agent_send

agent_query

Tools overview

Endpoints

Error codes

Channel resolution

On this page

Tools Reference

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

inputSchema (JSON Schema)

Tools overview

Endpoints

Error codes

Channel resolution

On this page