Slack MCP server request fails with AI_APICallError: tools.11.custom.name: String should match pattern '^[a-zA-Z0-9_-]{1,128}$' #3245

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1. github-actions commented on Oct 17, 2025

   

   github-actionsBot

   on Oct 17, 2025 – with GitHub Actions

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   This issue might be a duplicate of existing issues. Please check:

   • Invalid Schema errors on Azure OpenAI Models #441: Invalid Schema errors on Azure OpenAI Models - also deals with tool schema validation errors and naming patterns
   • bug: MCP - Invalid JSON Schema when using Docker MCP Gateway #650: bug: MCP - Invalid JSON Schema when using Docker MCP Gateway - similar JSON schema validation issues with MCP tools
   • AI_APICallError: GenerateContentRequest.tools[0].function_declarations[32].parameters. required[0]: property is not defined with Gemini API #3140: AI_APICallError: GenerateContentRequest.tools[0].function_declarations[32].parameters. required[0]: property is not defined with Gemini API - similar function declaration validation issues

   The error pattern you're seeing (tools.11.custom.name: String should match pattern '^[a-zA-Z0-9_-]{1,128}$') suggests that the Slack MCP server is providing tool names that don't conform to OpenCode's tool name validation pattern. This appears to be a broader issue with how OpenCode validates MCP tool names versus how different MCP servers define their tool names.

   Feel free to ignore if none of these address your specific case.
2. rekram1-node commented on Oct 17, 2025

   

   rekram1-node

   on Oct 17, 2025

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   Yeah we need to sanitize mcp server tools, this is because whatever provider you are using doesnt accept the format of the mcp server tools it has. So we need to "sanitize" the fields before sending them to specific providers
3. rekram1-node

   self-assigned this

   on Oct 17, 2025
4. mgryszko commented on Oct 17, 2025

   

   mgryszko

   on Oct 17, 2025

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   @rekram1-node will it be addressed in the next Opencode release?
5. rekram1-node commented on Oct 17, 2025

   

   rekram1-node

   on Oct 17, 2025

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   what provider are you using? Anthropic directly?

   Lmk which one and i can debug quicker

   normally these issues are with google models
6. mgryszko commented on Oct 17, 2025

   

   mgryszko

   on Oct 17, 2025

   Last edited by mgryszko

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   I was using Claude Sonnet 4.5 from GitHub Copilot.

   Here is my opencode.json config for reference:

       "slack": {
         "type": "local",
         "command": ["npx", "-y", "slack-mcp-server@latest", "--transport", "stdio"],
         "environment": {
           "SLACK_MCP_XOXC_TOKEN": "xoxc-xxx",
           "SLACK_MCP_XOXD_TOKEN": "xoxd-xxx"
         }
       }
   

   Claude Desktop configuration (claude_desktop_config):

       "slack": {
         "command": "npx",
         "args": [
           "-y",
           "slack-mcp-server@latest",
           "--transport",
           "stdio"
         ],
         "env": {
           "SLACK_MCP_XOXC_TOKEN": "xoxc-xxx",
           "SLACK_MCP_XOXD_TOKEN": "xoxd-xxx"
         }
       }
   
7. rekram1-node commented on Oct 17, 2025

   

   rekram1-node

   on Oct 17, 2025

   Last edited by rekram1-node

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   Ahh well if you were using anthropic then it should work, I guess we need special sanitization for copilot then.

   I need to familiarize myself with their requirements to see but I dont think this is terribly difficult to add
8. rekram1-node

   closed this as completedin #3842on Nov 3, 2025