# HarnessToolUseBlockStart
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Start payload for a tool use content block.

## Contents
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 ** name **   <a name="BedrockAgentCore-Type-HarnessToolUseBlockStart-name"></a>
The name of the tool being called.  
Type: String  
Length Constraints: Minimum length of 1. Maximum length of 64.  
Pattern: `[a-zA-Z0-9_-]+`   
Required: Yes

 ** toolUseId **   <a name="BedrockAgentCore-Type-HarnessToolUseBlockStart-toolUseId"></a>
The unique ID of this tool use.  
Type: String  
Length Constraints: Minimum length of 1. Maximum length of 64.  
Pattern: `[a-zA-Z0-9_-]+`   
Required: Yes

 ** serverName **   <a name="BedrockAgentCore-Type-HarnessToolUseBlockStart-serverName"></a>
The name of the MCP server providing this tool.  
Type: String  
Required: No

 ** type **   <a name="BedrockAgentCore-Type-HarnessToolUseBlockStart-type"></a>
The type of tool use.  
Type: String  
Valid Values: `tool_use | server_tool_use | mcp_tool_use`   
Required: No

## See Also
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For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/bedrock-agentcore-2024-02-28/HarnessToolUseBlockStart) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/bedrock-agentcore-2024-02-28/HarnessToolUseBlockStart) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/bedrock-agentcore-2024-02-28/HarnessToolUseBlockStart)