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    MCP Tools Reference: pubsub.googleapis.com

    Tool: publish

    Publish a series of one or more messages to an existing topic.

    Usage

    1. Create a new byte array to hold the message data.

    2. Populate the byte array with the message data.

    3. Call publish passing the topic name and the byte array.

    Important Notes

    • If the publish call returns NOT_FOUND, it likely means the topic does not exist. In this case, you should return an error.

    The following sample demonstrate how to use curl to invoke the publish MCP tool.

    Curl Request 
      
curl  
--location  
 'https://pubsub.googleapis.com/mcp' 
  
 \ 
--header  
 'content-type: application/json' 
  
 \ 
--header  
 'accept: application/json, text/event-stream' 
  
 \ 
--data  
 '{ 
 "method": "tools/call", 
 "params": { 
 "name": "publish", 
 "arguments": { 
 // provide these details according to the tool' 
s  
MCP  
specification  
 } 
  
 } 
,  
 "jsonrpc" 
:  
 "2.0" 
,  
 "id" 
:  
 1 
 } 
 '

    Input Schema

    Request for the Publish method.

    PublishRequest

    JSON representation 
     { 
 "projectId" 
 : 
 string 
 , 
 "topicId" 
 : 
 string 
 , 
 "messages" 
 : 
 [ 
 { 
 object (  PubsubMessage 
 
) 
 } 
 ] 
 }
    Fields
    projectId

    string

    Required. The project ID where the topic is located.
    topicId

    string

    Required. The ID of the topic where the messages will be published.
    messages[]

    object ( PubsubMessage )

    Required. The messages to publish.

    PubsubMessage

    JSON representation 
     { 
 "data" 
 : 
 string 
 , 
 "attributes" 
 : 
 { 
 string 
 : 
 string 
 , 
 ... 
 } 
 , 
 "messageId" 
 : 
 string 
 , 
 "publishTime" 
 : 
 string 
 , 
 "orderingKey" 
 : 
 string 
 }
    Fields
    data

    string ( bytes format)

    Optional. The message data field. If this field is empty, the message must contain at least one attribute.

    A base64-encoded string.
    attributes

    map (key: string, value: string)

    Optional. Attributes for this message. If this field is empty, the message must contain non-empty data. This can be used to filter messages on the subscription.

    An object containing a list of "key": value pairs. Example: { "name": "wrench", "mass": "1.3kg", "count": "3" } .
    messageId

    string

    ID of this message, assigned by the server when the message is published. Guaranteed to be unique within the topic. This value may be read by a subscriber that receives a PubsubMessage via a Pull call or a push delivery. It must not be populated by the publisher in a Publish call.
    publishTime

    string ( Timestamp format)

    The time at which the message was published, populated by the server when it receives the Publish call. It must not be populated by the publisher in a Publish call.

    Uses RFC 3339, where generated output will always be Z-normalized and use 0, 3, 6 or 9 fractional digits. Offsets other than "Z" are also accepted. Examples: "2014-10-02T15:01:23Z" , "2014-10-02T15:01:23.045123456Z" or "2014-10-02T15:01:23+05:30" .
    orderingKey

    string

    Optional. If non-empty, identifies related messages for which publish order should be respected. If a Subscription has enable_message_ordering set to true , messages published with the same non-empty ordering_key value will be delivered to subscribers in the order in which they are received by the Pub/Sub system. All PubsubMessage s published in a given PublishRequest must specify the same ordering_key value. For more information, see ordering messages .

    AttributesEntry

    JSON representation 
     { 
 "key" 
 : 
 string 
 , 
 "value" 
 : 
 string 
 }
    Fields
    key

    string

    value

    string

    Timestamp

    JSON representation 
     { 
 "seconds" 
 : 
 string 
 , 
 "nanos" 
 : 
 integer 
 }
    Fields
    seconds

    string ( int64 format)

    Represents seconds of UTC time since Unix epoch 1970-01-01T00:00:00Z. Must be between -62135596800 and 253402300799 inclusive (which corresponds to 0001-01-01T00:00:00Z to 9999-12-31T23:59:59Z).
    nanos

    integer

    Non-negative fractions of a second at nanosecond resolution. This field is the nanosecond portion of the duration, not an alternative to seconds. Negative second values with fractions must still have non-negative nanos values that count forward in time. Must be between 0 and 999,999,999 inclusive.

    Output Schema

    Response for the Publish method.

    PublishResponse

    JSON representation 
     { 
 "messageIds" 
 : 
 [ 
 string 
 ] 
 }
    Fields
    messageIds[]

    string

    Optional. The server-assigned ID of each published message, in the same order as the messages in the request. IDs are guaranteed to be unique within the topic.

    Tool Annotations

    Destructive Hint: ❌ | Idempotent Hint: ❌ | Read Only Hint: ❌ | Open World Hint: ✅
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