<p>If you&#39;re building a read-only tool with the Claude Agent SDK, make sure to mark it with `readOnlyHint: true`

This tells Claude Code it has no side effects and is safe to parallelize. Otherwise no other tool can run alongside it, essentially creating a &#34;serializing barrier&#34;!</p>

Lydia Hallie ✨

When building read-only tools with the Claude Agent SDK, marking them with `readOnlyHint: true` signals to Claude Code that the tool has no side effects and can safely run in parallel with other tools. Without this flag, the tool acts as a serializing barrier, preventing any other tool from running concurrently.

If you're building a read-only tool with the Claude Agent SDK, make sure to mark it with `readOnlyHint: true`

This tells Claude Code it has no side effects and is safe to parallelize. Otherwise no other tool can run alongside it, essentially creating a "serializing barrier"!

<p>If you're building a read-only tool with the Claude Agent SDK, make sure to mark it with `readOnlyHint: true`

This tells Claude Code it has no side effects and is safe to parallelize. Otherwise no other tool can run alongside it, essentially creating a &quot;serializing barrier&quot;!</p>