Follow Discord
Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
HomeDocsClaude Developer Platform 22 Oct 2026
One change · api

tools changedmanaged-agents/tools

Nearest release: v2.1.308, published 2 hours after this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

Recorded here
Lines+1added
Lines−1removed
From line 481 where the diff opens
First seen 14 Aug 2026 this site's first read of the page
Recorded edits23to this page, all time

The whole hunk

from line 481, old and new numbered
/
lines
from line 481
481481 
482482A custom tool's name can't start with `mcp__` or `ant__`, or match the name of a built-in agent tool. A request that breaks this rule returns a 400 error. An agent that already has a custom tool whose name starts with `ant__` accepts an update only if the update sends `tools` (csharp, go: `Tools`) without that name, so rename or remove the tool in your next update. A new session is refused with a 400 error if such a tool is on its agent (after any [overrides](https://platform.claude.com/docs/en/managed-agents/sessions#override-agent-configuration-for-a-session)), on an agent in the `predefined_agents` (java, php: `predefinedAgents`; csharp, go: `PredefinedAgents`) list of `subagents` (csharp, go: `Subagents`), or on an agent in the `predefined_agents` (java, php: `predefinedAgents`; csharp, go: `PredefinedAgents`) list of `workflows` (csharp, go: `Workflows`). Sessions that already exist aren't affected.
483483 
484The agent calls its custom tools during a session. To receive the calls and return results, see [Session event stream](https://platform.claude.com/docs/en/managed-agents/events-and-streaming#handling-custom-tool-calls).
484The agent calls its custom tools during a session. To receive the calls and return results, see [Answer tool calls that pause the session](https://platform.claude.com/docs/en/managed-agents/events-and-streaming#handling-custom-tool-calls).
485485 
486486For sessions that run in a self-hosted sandbox, the environment worker can [serve custom tools from the sandbox](https://platform.claude.com/docs/en/managed-agents/self-hosted-sandboxes-custom-tools). These can include tools that wrap an MCP server inside your network.
487487 
Feedback