[FEATURE] Collapsible/truncated display for large MCP tool input parameters

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When MCP tools accept large string parameters (e.g., a doc_write tool with a content field containing a full markdown document), Claude Code displays the entire parameter value in the terminal. This floods the screen with content the user already knows about (since they typically just reviewed or discussed it in the conversation).

This is different from the output display issue — it's specifically about input parameters to MCP tool calls being rendered in full.

Example: writing a 3KB markdown document via an MCP doc_write tool renders all 3KB inline in the terminal, pushing useful context off-screen.

Previously reported as #11437, #20619, #21495, #21818 — all auto-closed as duplicates of each other with no resolution.

Proposed Solution

Option 1 (preferred): Collapse large parameters by default

For any MCP tool input parameter exceeding a threshold (e.g., 500 chars), show a summary line with expand option:

zero - doc_write (MCP)(path: "coordination/state.md", content: [2.5KB markdown] ▸, message: "Update state")

ctrl+o or click to expand the full content (consistent with existing expand behavior for outputs).

Option 2: MCP tool schema annotation

Allow MCP servers to hint that a parameter is large/verbose via a schema extension:

{
  "name": "content",
  "type": "string",
  "x-display": "collapsed"
}

Claude Code would respect this hint and collapse the parameter by default.

Option 3: Global verbosity setting

// .claude/settings.json
{
  "toolInputDisplayMode": "compact"  // "compact" | "full"
}

Alternative Solutions

Per-server or per-tool display config in settings.json, e.g.:

{
  "mcpServers": {
    "zero": {
      "displayMode": "compact"
    }
  }
}

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

A typical session involves 5-10 doc_write calls updating state docs, plans, and briefs — each 1-5KB of markdown. The terminal becomes a wall of document content rather than a readable session log. The user has to scroll extensively to find Claude's actual responses between the tool calls.

Additional Context

This is a long-standing pain point reported across multiple issues (#11437, #20619, #21495, #21818) that were all auto-closed as duplicates of each other. None were actually resolved. The feature would significantly improve the experience for any MCP server that writes documents, posts comments, or handles large text payloads.