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    MCP Tools Reference: pubsub.googleapis.com

    Tool: publish

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

    Parameters

    • topic : The name of the topic to publish to in the format projects/{project_id}/topics/{topic_name} .

    • messages : A list of one or more messages to publish. Each message must be of type bytes . If you are given a string, you must first convert it to bytes.

    Returns

    • A PublishResponse object containing the message IDs of the published messages, if successful.

    • A NOT_FOUND error if the topic does not exist.

    Usage

    1. Ensure that the topic exists by calling get_topic .

    2. If the topic does not exist, return an error.

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

    4. Populate the byte array with the message data.

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

    Important Notes

    • A project ID, topic name, and message data must be provided.

    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 
     { 
 "topic" 
 : 
 string 
 , 
 "messages" 
 : 
 [ 
 { 
 object (  PubsubMessage 
 
) 
 } 
 ] 
 }
    Fields
    topic

    string

    Required. The messages in the request will be published on this topic. Format is projects/{project}/topics/{topic} .
    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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