MCP Tools Reference: agentregistry.googleapis.com

Tool: search_mcp_servers

Perform a keyword or prefix search to discover MCP servers. Use this to find servers based on the specific tools they offer, their descriptions, or natural language queries.

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

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

Input Schema

Message for searching MCP Servers

SearchMcpServersRequest

JSON representation 
{
  "parent": string,
  "searchString": string,
  "pageSize": integer,
  "pageToken": string
}
Fields
parent

string

Required. Parent value for SearchMcpServersRequest. Format: projects/{project}/locations/{location}.
searchString

string

Optional. Search criteria used to select the MCP Servers to return. If no search criteria is specified then all accessible MCP Servers will be returned.

Search expressions can be used to restrict results based upon searchable fields, where the operators can be used along with the suffix wildcard symbol *. See instructions for more details.

Allowed operators: =, :, NOT, AND, OR, and ().

Searchable fields:

Field = : * Keyword Search
mcpServerId Yes Yes Yes Included
name No Yes Yes Included
displayName No Yes Yes Included

Examples:

  • mcpServerId=urn:mcp:projects-123:projects:123:locations:us-central1:agentregistry:services:service-id to find the MCP Server with the specified MCP Server ID.
  • name:important to find MCP Servers whose name contains important as a word.
  • displayName:works* to find MCP Servers whose display name contains words that start with works.
  • planner OR booking to find MCP Servers whose metadata contains the words planner or booking.
  • mcpServerId:service-id AND (displayName:planner OR displayName:booking) to find MCP Servers whose MCP Server ID contains service-id and whose display name contains planner or booking.
pageSize

integer

Optional. The maximum number of search results to return per page. The page size is capped at 100, even if a larger value is specified. A negative value will result in an INVALID_ARGUMENT error. If unspecified or set to 0, a default value of 20 will be used. The server may return fewer results than requested.
pageToken

string

Optional. If present, retrieve the next batch of results from the preceding call to this method. page_token must be the value of next_page_token from the previous response. The values of all other method parameters, must be identical to those in the previous call.

Output Schema

Message for response to searching MCP Servers

SearchMcpServersResponse

JSON representation 
{
  "mcpServers": [
    {
      object (McpServer)
    }
  ],
  "nextPageToken": string
}
Fields
mcpServers[]

object (McpServer)

A list of McpServers that match the search_string.
nextPageToken

string

If there are more results than those appearing in this response, then next_page_token is included. To get the next set of results, call this method again using the value of next_page_token as page_token.

McpServer

JSON representation 
{
  "name": string,
  "mcpServerId": string,
  "displayName": string,
  "description": string,
  "interfaces": [
    {
      object (Interface)
    }
  ],
  "tools": [
    {
      object (Tool)
    }
  ],
  "createTime": string,
  "updateTime": string,
  "attributes": {
    string: {
      object
    },
    ...
  }
}
Fields
name

string

Identifier. The resource name of the MCP Server. Format: projects/{project}/locations/{location}/mcpServers/{mcp_server}.
mcpServerId

string

Output only. A stable, globally unique identifier for MCP Servers.
displayName

string

Output only. The display name of the MCP Server.
description

string

Output only. The description of the MCP Server.
interfaces[]

object (Interface)

Output only. The connection details for the MCP Server.
tools[]

object (Tool)

Output only. Tools provided by the MCP Server.
createTime

string (Timestamp format)

Output only. Create time.

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".
updateTime

string (Timestamp format)

Output only. Update time.

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".
attributes

map (key: string, value: object (Struct format))

Output only. Attributes of the MCP Server. Valid values:

  • agentregistry.googleapis.com/system/RuntimeIdentity: {"principal": "principal://..."} - the runtime identity associated with the MCP Server.
  • agentregistry.googleapis.com/system/RuntimeReference: {"uri": "//..."}
  • the URI of the underlying resource hosting the MCP Server, for example, the GKE Deployment.

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

Interface

JSON representation 
{
  "url": string,
  "protocolBinding": enum (ProtocolBinding)
}
Fields
url

string

Required. The destination URL.
protocolBinding

enum (ProtocolBinding)

Required. The protocol binding of the interface.

Tool

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

string

Output only. Human-readable name of the tool.
description

string

Output only. Description of what the tool does.
annotations

object (Annotations)

Output only. Annotations associated with the tool.

Annotations

JSON representation 
{
  "title": string,
  "destructiveHint": boolean,
  "idempotentHint": boolean,
  "openWorldHint": boolean,
  "readOnlyHint": boolean
}
Fields
title

string

Output only. A human-readable title for the tool.
destructiveHint

boolean

Output only. If true, the tool may perform destructive updates to its environment. If false, the tool performs only additive updates. NOTE: This property is meaningful only when read_only_hint == false Default: true
idempotentHint

boolean

Output only. If true, calling the tool repeatedly with the same arguments will have no additional effect on its environment. NOTE: This property is meaningful only when read_only_hint == false Default: false
openWorldHint

boolean

Output only. If true, this tool may interact with an "open world" of external entities. If false, the tool's domain of interaction is closed. For example, the world of a web search tool is open, whereas that of a memory tool is not. Default: true
readOnlyHint

boolean

Output only. If true, the tool does not modify its environment. Default: false

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.

AttributesEntry

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

string
value

object (Struct format)

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. 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. The kind of value. kind can be only one of the following:
nullValue

null

Represents a JSON null.
numberValue

number

Represents a JSON number. Must not be NaN, Infinity or -Infinity, since those are not supported in JSON. This also cannot represent large Int64 values, since JSON format generally does not support them in its number type.
stringValue

string

Represents a JSON string.
boolValue

boolean

Represents a JSON boolean (true or false literal in JSON).
structValue

object (Struct format)

Represents a JSON object.
listValue

array (ListValue format)

Represents a JSON array.

ListValue

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

value (Value format)

Repeated field of dynamically typed values.

Tool Annotations

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