[BUG] tools[21].function.name': string too long. Expected a string with maximum length 64, but got a string with length 65 instead.

Description

Tool name is too long. This was taken from logs.
Opencode does not send any error message to TUI, it just will die silently.
And it also do not process any more request when tool name is too long, even when unrelated to MCP servers.

Might be related to this: https://github.com/sst/opencode/blob/a0541ba57aebcdb21c36540f0efd8a251fdbc2b8/packages/opencode/src/mcp/index.ts#L207-L209

This generates tool name from mcp name + tool name.
It would be better to set that max size to 64 characters to fix this issue.

Same issue was in ravitemer/mcphub.nvim#243 and limiting tool length fixed it. In difference, mcphub.nvim throws an error to user.

OpenCode version

0.15.23

Steps to reproduce

Change MCP server to long name (60+ characters)
Try to use opencode with any MCP server
Opencode will just die silently after running "generating" for second

Screenshot and/or share link

Operating System

Pop_os 22.04.

Terminal

Kitty, tmux, nvim with sidekick.nvim

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

Slack MCP server request fails with AI_APICallError: tools.11.custom.name: String should match pattern '^[a-zA-Z0-9_-]{1,128}$' #3245: Similar MCP tool naming issue with string pattern validation - Slack MCP server fails with 'String should match pattern' error for tool names
[mcp] Can't submit a message using Anthropic Sonnet 4.5 and MCP tools due to "String should match pattern" #3354: MCP tools failing with 'String should match pattern' error when using Anthropic Sonnet 4.5 and MCP servers

Both issues involve MCP server tool naming validation problems, though #3523 specifically mentions the 64-character length limit while the others mention pattern validation. The root cause appears related to how OpenCode generates tool names from MCP server names + tool names.

Feel free to ignore if none of these address your specific case.

What provider gave that error?

What provider gave that error?

Company internal MCP server. Tool names are generated and limited to ~50 characters.

@Racle

@Racle but that error comes from an inference provider I thought, I don't think the ai sdk is throwing it (could be wrong tho)

What inference provider was it? Openai? Google?

@Racle but that error comes from an inference provider I thought, I don't think the ai sdk is throwing it (could be wrong tho)

What inference provider was it? Openai? Google?

Test MCP config what can be used to test this:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "chrome-devtools-aaaaaaaaaaaaaaaaaaaaa": {
      "type": "local",
      "command": ["npx", "chrome-devtools-mcp@latest"]
    }
  }
}

I'm using GitHub Copilot GPT-4.1 as that is the only one I currently have access.

I see the error in opencode log files (running this as opencode --log-level DEBUG ), but terminal client just dies silently. There is no error message.

INFO  2025-10-29T16:10:59 +1ms service=session.prompt session=ses_5cf4368afffewe4wL4auBcU6OA type=error part
ERROR 2025-10-29T16:10:59 +1ms service=session.prompt session=ses_5cf4368afffewe4wL4auBcU6OA error=Invalid 'tools[29].function.name': string too long. Expected a string with maximum length 64, but got a string with length 65 instead. process

good to know thanks!

I encounter similar issues when using any of the gpt models (from copilot) and docker mcp enabled. Other models (claude/gemini 2.5 pro) works fine.

Yeah if you are using too many tools they get upset, im not sure what we can do for u besides truncate the tools and give u an error or warning

I'd like to work on this. The fix truncates the combined MCP server + tool name to 64 characters and logs a warning when truncation occurs.

PR: #15595

Samem problem here when using latest GPT-5.3 Codex in OC 1.2.18

"Invalid 'input[].call_id': string too long. Expected a string with maximum length 64, but got a string with length 2507 instead."

I keep getting this error

Invalid 'input[202].call_id': string too long. Expected a string with maximum length 64, but got a string with length 65 instead.

using model: nvidia/moonshotai/kimi-k2.5, but also with openai/gpt5.3-codex

It seems this bug mainly concers longr sessions. Started over with a new session with Codex-5.3 and there error does not appear.

fix: resolve 4 bugs — payload bloat, MCP subagents, tool names, token…

To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.

fix(mcp): truncate tool names exceeding 64 chars to fit provider limit

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[BUG] tools[21].function.name': string too long. Expected a string with maximum length 64, but got a string with length 65 instead. #3523

Description

OpenCode version

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Operating System

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[BUG] tools[21].function.name': string too long. Expected a string with maximum length 64, but got a string with length 65 instead. #3523

Description

Description

OpenCode version

Steps to reproduce

Screenshot and/or share link

Operating System

Terminal

Activity

github-actions commented on Oct 29, 2025

rekram1-node commented on Oct 29, 2025

Racle commented on Oct 29, 2025

rekram1-node commented on Oct 29, 2025

Racle commented on Oct 29, 2025

rekram1-node commented on Oct 29, 2025

faizhasim commented on Nov 13, 2025

rekram1-node commented on Nov 13, 2025

Br1an67 commented on Mar 1, 2026

morpheus9393 commented on Mar 6, 2026

EvanDataForge commented on Mar 7, 2026

morpheus9393 commented on Mar 7, 2026

github-actions commented on Jul 3, 2026

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