> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# exceptions

# `fastmcp.exceptions`

Custom exceptions for FastMCP.

## Classes

### `FastMCPDeprecationWarning` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L13" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Deprecation warning for FastMCP APIs.

Subclass of DeprecationWarning so that standard warning filters
still apply, but FastMCP can selectively enable its own warnings
without affecting other libraries in the process.

### `FastMCPError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L22" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Base error for FastMCP.

### `ValidationError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L30" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Error in validating parameters or return values.

### `ResourceError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L34" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Error in resource operations.

### `ToolError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L38" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Error in tool operations.

### `PromptError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L42" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Error in prompt operations.

### `InvalidSignature` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L46" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Invalid signature for use with FastMCP.

### `ClientError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L50" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Error in client operations.

### `NotFoundError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L54" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Object not found.

### `DisabledError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L58" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Object is disabled.

### `AuthorizationError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L62" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Error when authorization check fails.