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    MCP tools reference: storage.googleapis.com

    Tool: read_object

    Reads a blob object from Cloud Storage.

    Use this tool for binary files, such as images, PDFs, and zip archives.

    This tool has the following constraints and behaviors:

    • Size limit: The maximum supported file size is 8MiB. Requests for larger objects will fail with an OutOfRange error.
    • Text or binary: For valid UTF-8 text files, use read_text instead, as it consumes fewer tokens.

    The following example shows how to use curl to invoke the read_object MCP tool:

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

    Input schema

    Request message for ReadObject.

    ReadObjectRequest

    JSON representation 
     { 
 "bucketName" 
 : 
 string 
 , 
 "objectName" 
 : 
 string 
 , 
 "contentType" 
 : 
 string 
 }
    Fields
    bucketName

    string

    Required. Cloud Storage bucket name.
    objectName

    string

    Required. Cloud Storage object name.
    contentType

    string

    Optional. The IANA media type of the object (for example, application/pdf , image/png ). Provide contentType only if the object name or context suggests a specific format.

    Output schema

    CallToolResponse

    JSON representation 
     { 
 "common" 
 : 
 { 
 object (  ResponseFields 
 
) 
 } 
 , 
 "content" 
 : 
 [ 
 { 
 object (  Content 
 
) 
 } 
 ] 
 , 
 "structuredContent" 
 : 
 { 
 object 
 } 
 , 
 "isError" 
 : 
 boolean 
 }
    Fields
    common

    object ( ResponseFields )

    content[]

    object ( Content )

    structuredContent

    object ( Struct format)

    If the tool defines an output schema, this field is populated. Clients that support structured output should ignore the content field above if this field is set.
    isError

    boolean

    Optional.

    ResponseFields

    JSON representation 
     { 
 "instructions" 
 : 
 string 
 , 
 "metadata" 
 : 
 { 
 object 
 } 
 , 
 "dependentRequests" 
 : 
 { 
 string 
 : 
 { 
 object (  ServerInitiatedRequest 
 
) 
 } 
 , 
 ... 
 } 
 , 
 "resumeData" 
 : 
 { 
 object 
 } 
 }
    Fields
    instructions

    string

    Optional. Sent only on the initial response on any RPC.
    metadata

    object ( Struct format)

    Escape hatch for arbitrary side-channel data.
    dependentRequests

    map (key: string, value: object ( ServerInitiatedRequest ))

    Dependent requests. This field indicates that the request is incomplete. The client must try its request again with the results of these dependent requests in the dependent_responses field.

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

    object ( Struct format)

    State for the client to echo back in subsequent RPCs for the same persistent request.

    Struct

    JSON representation 
     { 
 "fields" 
 : 
 { 
 string 
 : 
 value 
 , 
 ... 
 } 
 }
    Fields
    fields

    map (key: string, value: value ( Value format))

    Unordered map of dynamically typed values.

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

    FieldsEntry

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

    string

    value

    value ( Value format)

    Value

    JSON representation 
     { 
 // Union field kind 
can be only one of the following: 
 "nullValue" 
 : 
 null 
 , 
 "numberValue" 
 : 
 number 
 , 
 "stringValue" 
 : 
 string 
 , 
 "boolValue" 
 : 
 boolean 
 , 
 "structValue" 
 : 
 { 
 object 
 } 
 , 
 "listValue" 
 : 
 array 
 // End of list of possible types for union field kind 
. 
 }
    Fields
    Union field kind . This field can be only one of the following values:
    nullValue

    null

    Represents a null value.

    numberValue

    number

    Represents a double value.

    stringValue

    string

    Represents a string value.

    boolValue

    boolean

    Represents a boolean value.

    structValue

    object ( Struct format)

    Represents a structured value.

    listValue

    array ( ListValue format)

    Represents a repeated Value .

    ListValue

    JSON representation 
     { 
 "values" 
 : 
 [ 
 value 
 ] 
 }
    Fields
    values[]

    value ( Value format)

    Repeated field of dynamically typed values.

    DependentRequestsEntry

    JSON representation 
     { 
 "key" 
 : 
 string 
 , 
 "value" 
 : 
 { 
 object (  ServerInitiatedRequest 
 
) 
 } 
 }
    Fields
    key

    string

    value

    object ( ServerInitiatedRequest )

    ServerInitiatedRequest

    JSON representation 
     { 
 "samplingCreateMessage" 
 : 
 { 
 object (  SamplingCreateMessageRequest 
 
) 
 } 
 , 
 "listRootsRequest" 
 : 
 { 
 object ( ListRootsRequest 
) 
 } 
 , 
 "notifyOnRootListUpdate" 
 : 
 boolean 
 , 
 "elicitRequest" 
 : 
 { 
 object (  ElicitRequest 
 
) 
 } 
 }
    Fields
    samplingCreateMessage

    object ( SamplingCreateMessageRequest )

    Sampling, as per https://modelcontextprotocol.io/specification/2025-03-26/client/sampling .
    listRootsRequest

    object ( ListRootsRequest )

    Root list request, as per https://modelcontextprotocol.io/specification/2025-03-26/client/roots .
    notifyOnRootListUpdate

    boolean

    elicitRequest

    object ( ElicitRequest )

    Elicitations, as per https://modelcontextprotocol.io/specification/2025-06-18/client/elicitation .

    SamplingCreateMessageRequest

    JSON representation 
     { 
 "messages" 
 : 
 [ 
 { 
 object (  SamplingMessage 
 
) 
 } 
 ] 
 , 
 "modelPreferences" 
 : 
 { 
 object (  ModelPreferences 
 
) 
 } 
 , 
 "systemPrompt" 
 : 
 string 
 , 
 "includeContext" 
 : 
 enum ( IncludeContext 
) 
 , 
 "temperature" 
 : 
 number 
 , 
 "maxTokens" 
 : 
 integer 
 , 
 "stopSequence" 
 : 
 [ 
 string 
 ] 
 }
    Fields
    messages[]

    object ( SamplingMessage )

    modelPreferences

    object ( ModelPreferences )

    Optional.
    systemPrompt

    string

    Optional.
    includeContext

    enum ( IncludeContext )

    Optional.
    temperature

    number

    Optional.
    maxTokens

    integer

    Optional.
    stopSequence[]

    string

    Optional.

    SamplingMessage

    JSON representation 
     { 
 "role" 
 : 
 enum ( Role 
) 
 , 
 "text" 
 : 
 { 
 object (  TextContent 
 
) 
 } 
 , 
 "image" 
 : 
 { 
 object (  ImageContent 
 
) 
 } 
 , 
 "audio" 
 : 
 { 
 object (  AudioContent 
 
) 
 } 
 }
    Fields
    role

    enum ( Role )

    Which role is sending the message.
    text

    object ( TextContent )

    Populate exactly one of these fields. (This implementation avoids "oneof" to prevent forward-compatibility problems.)
    image

    object ( ImageContent )

    audio

    object ( AudioContent )

    TextContent

    JSON representation 
     { 
 "text" 
 : 
 string 
 , 
 "annotations" 
 : 
 { 
 object (  Annotations 
 
) 
 } 
 }
    Fields
    text

    string

    annotations

    object ( Annotations )

    Optional.

    Annotations

    JSON representation 
     { 
 "audience" 
 : 
 [ 
 enum ( Role 
) 
 ] 
 , 
 "priority" 
 : 
 number 
 }
    Fields
    audience[]

    enum ( Role )

    priority

    number

    Must be in range [0,1].

    ImageContent

    JSON representation 
     { 
 "data" 
 : 
 string 
 , 
 "mimeType" 
 : 
 string 
 , 
 "annotations" 
 : 
 { 
 object (  Annotations 
 
) 
 } 
 }
    Fields
    data

    string ( bytes format)

    A base64-encoded string.
    mimeType

    string

    annotations

    object ( Annotations )

    Optional.

    AudioContent

    JSON representation 
     { 
 "data" 
 : 
 string 
 , 
 "mimeType" 
 : 
 string 
 , 
 "annotations" 
 : 
 { 
 object (  Annotations 
 
) 
 } 
 }
    Fields
    data

    string ( bytes format)

    A base64-encoded string.
    mimeType

    string

    annotations

    object ( Annotations )

    Optional.

    ModelPreferences

    JSON representation 
     { 
 "hints" 
 : 
 [ 
 { 
 object (  ModelHint 
 
) 
 } 
 ] 
 , 
 "intelligencePriority" 
 : 
 number 
 , 
 "speedPriority" 
 : 
 number 
 , 
 "costPriority" 
 : 
 number 
 }
    Fields
    hints[]

    object ( ModelHint )

    intelligencePriority

    number

    speedPriority

    number

    costPriority

    number

    ModelHint

    JSON representation 
     { 
 "name" 
 : 
 string 
 }
    Fields
    name

    string

    Optional.

    ElicitRequest

    JSON representation 
     { 
 "message" 
 : 
 string 
 , 
 "requestedSchema" 
 : 
 { 
 string 
 : 
 { 
 object (  PrimitiveSchemaDefinition 
 
) 
 } 
 , 
 ... 
 } 
 , 
 "requiredFields" 
 : 
 [ 
 string 
 ] 
 }
    Fields
    message

    string

    Message to present to user. Required.
    requestedSchema

    map (key: string, value: object ( PrimitiveSchemaDefinition ))

    An object containing a list of "key": value pairs. For example: { "name": "wrench", "mass": "1.3kg", "count": "3" } .
    requiredFields[]

    string

    RequestedSchemaEntry

    JSON representation 
     { 
 "key" 
 : 
 string 
 , 
 "value" 
 : 
 { 
 object (  PrimitiveSchemaDefinition 
 
) 
 } 
 }
    Fields
    key

    string

    value

    object ( PrimitiveSchemaDefinition )

    PrimitiveSchemaDefinition

    JSON representation 
     { 
 "stringSchema" 
 : 
 { 
 object (  StringSchema 
 
) 
 } 
 , 
 "numberSchema" 
 : 
 { 
 object (  NumberSchema 
 
) 
 } 
 , 
 "booleanSchema" 
 : 
 { 
 object (  BooleanSchema 
 
) 
 } 
 , 
 "enumSchema" 
 : 
 { 
 object (  EnumSchema 
 
) 
 } 
 }
    Fields
    stringSchema

    object ( StringSchema )

    Exactly one of these fields is present. (This implementation avoids "oneof" to prevent forward-compatibility problems.)
    numberSchema

    object ( NumberSchema )

    booleanSchema

    object ( BooleanSchema )

    enumSchema

    object ( EnumSchema )

    StringSchema

    JSON representation 
     { 
 "title" 
 : 
 string 
 , 
 "description" 
 : 
 string 
 , 
 "minLength" 
 : 
 string 
 , 
 "maxLength" 
 : 
 string 
 , 
 "format" 
 : 
 enum ( Format 
) 
 }
    Fields
    title

    string

    description

    string

    minLength

    string

    maxLength

    string

    format

    enum ( Format )

    NumberSchema

    JSON representation 
     { 
 "title" 
 : 
 string 
 , 
 "description" 
 : 
 string 
 , 
 "minimum" 
 : 
 string 
 , 
 "maximum" 
 : 
 string 
 }
    Fields
    title

    string

    description

    string

    minimum

    string

    maximum

    string

    BooleanSchema

    JSON representation 
     { 
 "title" 
 : 
 string 
 , 
 "description" 
 : 
 string 
 , 
 "default" 
 : 
 boolean 
 }
    Fields
    title

    string

    description

    string

    default

    boolean

    EnumSchema

    JSON representation 
     { 
 "title" 
 : 
 string 
 , 
 "description" 
 : 
 string 
 , 
 "enumList" 
 : 
 [ 
 string 
 ] 
 , 
 "enumNames" 
 : 
 [ 
 string 
 ] 
 }
    Fields
    title

    string

    description

    string

    enumList[]

    string

    enumNames[]

    string

    Content

    JSON representation 
     { 
 "text" 
 : 
 { 
 object (  TextContent 
 
) 
 } 
 , 
 "image" 
 : 
 { 
 object (  ImageContent 
 
) 
 } 
 , 
 "audio" 
 : 
 { 
 object (  AudioContent 
 
) 
 } 
 , 
 "embeddedResource" 
 : 
 { 
 object (  EmbeddedResource 
 
) 
 } 
 , 
 "resourceLink" 
 : 
 { 
 object (  Resource 
 
) 
 } 
 }
    Fields
    text

    object ( TextContent )

    Unstructured result contents. If the tool does not define an output schema, at least one of these fields is populated. If the tool defines an output schema, the structured_content field is populated instead. One of these fields might still be populated for backward compatibility.

    Populate no more than one of these fields. (This implementation avoids "oneof" to prevent forward-compatibility problems.)
    image

    object ( ImageContent )

    audio

    object ( AudioContent )

    embeddedResource

    object ( EmbeddedResource )

    resourceLink

    object ( Resource )

    EmbeddedResource

    JSON representation 
     { 
 "contents" 
 : 
 { 
 object (  ResourceContents 
 
) 
 } 
 , 
 "annotations" 
 : 
 { 
 object (  Annotations 
 
) 
 } 
 }
    Fields
    contents

    object ( ResourceContents )

    annotations

    object ( Annotations )

    Optional.

    ResourceContents

    JSON representation 
     { 
 "uri" 
 : 
 string 
 , 
 "mimeType" 
 : 
 string 
 , 
 "text" 
 : 
 string 
 , 
 "blob" 
 : 
 string 
 }
    Fields
    uri

    string

    mimeType

    string

    text

    string

    Populate exactly one of these fields. (This implementation avoids "oneof" to prevent forward-compatibility problems.)
    blob

    string ( bytes format)

    A base64-encoded string.

    Resource

    JSON representation 
     { 
 "uri" 
 : 
 string 
 , 
 "name" 
 : 
 string 
 , 
 "title" 
 : 
 string 
 , 
 "description" 
 : 
 string 
 , 
 "mimeType" 
 : 
 string 
 , 
 "annotations" 
 : 
 { 
 object (  Annotations 
 
) 
 } 
 , 
 "size" 
 : 
 string 
 }
    Fields
    uri

    string

    name

    string

    title

    string

    description

    string

    Optional.
    mimeType

    string

    Optional.
    annotations

    object ( Annotations )

    Optional.
    size

    string

    Optional.

    Tool Annotations

    Destructive hint: ❌ | Idempotent hint: ✅ | Read-only hint: ✅ | Open-world hint: ❌
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