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47 lines
2.3 KiB
Text
47 lines
2.3 KiB
Text
---
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title: Client Roots
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sidebarTitle: Roots
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description: Tell servers which local paths your client can reach.
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icon: folder-tree
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---
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import { VersionBadge } from '/snippets/version-badge.mdx'
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<VersionBadge version="2.0.0" />
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Use this when you need to tell servers what local resources the client has access to.
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A root is a path your client is willing to expose — a project directory, a workspace, a document store. Servers read them to scope their work, so a tool that searches files searches where you pointed it, and a server that gets no roots has to ask the user for paths instead. Roots describe where the client can reach; the server takes them as its working boundary.
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Register them once with `roots=`, and the client answers however the server asks. A handshake-era server pushes a `roots/list` request down the open session and reads the reply mid-call; a modern (`2026-07-28`) server has no such channel, so it returns a roots request and `fastmcp.Client` fulfils it from the same registration and re-issues the call with the answer attached. The default `mode="auto"` negotiates whichever era the server speaks, so the examples below work on either — see [protocol negotiation](/clients/client#protocol-negotiation) for how that choice is made, and [the guard pattern](/servers/elicitation#sampling-and-roots) for how a server issues the modern form.
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## Static Roots
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When the paths are known up front, pass them as a list. The client holds them for the life of the connection and hands back the same set every time a server asks.
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```python
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from fastmcp import Client
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client = Client(
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"my_mcp_server.py",
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roots=["file:///path/to/root1", "file:///path/to/root2"]
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)
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```
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## Dynamic Roots
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Pass a callback instead when the roots depend on something the client learns at runtime, such as the workspace the user has open. It runs at the moment a server asks, on either route, and receives the request context so you can see which request it is answering:
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```python
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from fastmcp import Client
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from fastmcp.client.roots import RequestContext
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async def roots_callback(context: RequestContext) -> list[str]:
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print(f"Server requested roots (Request ID: {context.request_id})")
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return ["file:///path/to/root1", "file:///path/to/root2"]
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client = Client(
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"my_mcp_server.py",
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roots=roots_callback
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)
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```
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