MCP plugin tool names exceed 64-character API limit

Bug Description

When using MCP plugins with longer names (e.g., atlassian-mcp-remote), the generated tool names exceed the Claude API's 64-character limit for tool_name fields, causing a 400 error.

Error Message

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.6.content.0.tool_result.content.3.tool_reference.tool_name: String should have at most 64 characters"}}

Root Cause

The plugin tool naming convention mcp__plugin_<plugin-name>_<server-name>__<tool> produces names that are too long. For example, the atlassian-mcp-remote plugin with server name atlassian produces a prefix of:

mcp__plugin_atlassian-mcp-remote_atlassian__

This prefix alone is 45 characters, leaving only 19 characters for the actual tool name. Many Atlassian tools have longer names, causing them to exceed 64 characters.

Examples of tool names exceeding the limit

| Tool Name | Length |
|---|---|
| mcp__plugin_atlassian-mcp-remote_atlassian__getJiraProjectIssueTypesMetadata | 77 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getAccessibleAtlassianResources | 76 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getConfluencePageFooterComments | 76 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getConfluencePageInlineComments | 76 |
| mcp__plugin_atlassian-mcp-remote_atlassian__createConfluenceFooterComment | 74 |
| mcp__plugin_atlassian-mcp-remote_atlassian__createConfluenceInlineComment | 74 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getConfluencePageDescendants | 73 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getJiraIssueRemoteIssueLinks | 73 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getTransitionsForJiraIssue | 71 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getPagesInConfluenceSpace | 70 |
| mcp__plugin_atlassian-mcp-remote_atlassian__searchJiraIssuesUsingJql | 69 |
| mcp__plugin_atlassian-mcp-remote_atlassian__searchConfluenceUsingCql | 69 |
| mcp__plugin_atlassian-mcp-remote_atlassian__getVisibleJiraProjects | 66 |
| mcp__plugin_atlassian-mcp-remote_atlassian__addCommentToJiraIssue | 65 |
| mcp__plugin_atlassian-mcp-remote_atlassian__addWorklogToJiraIssue | 65 |

Impact

• The error occurs when Claude Code attempts to call one of these long-named MCP tools during a conversation
• In some cases, once the error occurs it can brick the conversation, requiring a new session
• Workaround: Disable the offending plugin in ~/.claude/settings.json

Suggested Fix

The tool naming system should enforce the 64-character limit. Options:

1. Truncate or hash long prefixes to stay within the limit
2. Use shorter aliases for the plugin/server namespace (e.g., mcp__atl__ instead of mcp__plugin_atlassian-mcp-remote_atlassian__)
3. Validate tool names at registration time and warn or reject names exceeding 64 characters

Environment

• Claude Code version: 2.1.19
• OS: macOS (Darwin 24.6.0)
• Plugin: atlassian-mcp-remote (from heyjobs-plugins marketplace)