[BUG] Read tool (Claude Code Desktop): optional `pages` sent as "" fails validation on non-PDF

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

On Claude Code Desktop, invoking Read on a non-PDF file (e.g. .md) fails when the optional pages argument is serialized as an empty string ("") instead of being omitted.

The tool rejects the call before returning file content:

Invalid pages parameter: "". Use formats like "1-5", "3", or "10-20". Pages are 1-indexed.

This breaks normal workflows that frequently Read Markdown (e.g. skill/agent prompts under ~/.claude/skills/.../agents/*.md). The failure repeats whenever the client/model emits pages: "".

What Should Happen?

• For non-PDF files, pages should be irrelevant: ignore pages, or treat it as unset.
• If pages is "" or whitespace-only, normalize to unset and do not run the PDF page-range validator.

Expected: Read succeeds for .md / text / code when only file_path, limit, and offset are meaningful; optional pages must not break the call when empty.

Error Messages/Logs

Read
proactive-scout.md
file_path: C:\Users\AliceDev\.claude\skills\contoso-workflow\agents\proactive-scout.md
limit: 2000
offset: 0
pages:
Invalid pages parameter: "". Use formats like "1-5", "3", or "10-20". Pages are 1-indexed.

Steps to Reproduce

1. Open Claude Code Desktop on Windows.
2. In a session that can use tools, trigger Read on any Markdown file (e.g. a skill agents/*.md).
3. Ensure the serialized tool input includes pages as an empty string (the UI/log shows pages: with no value, or pages: "").
4. Observe: validation error instead of file contents.

Note: Reproduction may depend on how the desktop client builds tool JSON (optional fields defaulting to ""). The bug is the strict validation on empty string rather than treating it as omitted.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude for Windows Claude 1.5354.0 (9a9e3d) 2026-04-29T01:14:34.000Z

Platform

Other

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• Product: Claude Code Desktop (Windows).
• Suggested fix: coerce pages === "" → unset before validation; optionally skip pages validation entirely for non-PDF MIME types.
• Related: optional tool fields often serialize as empty strings; validating "" like an invalid page range is overly strict.