Module alias 

Tool aliasing middleware for the proxy.

Rewrites tool names in list responses and call requests based on per-backend alias configuration. This lets operators expose backend tools under different names without modifying the backends themselves.

How it works

Aliasing maintains a bidirectional mapping between original and aliased names (stored in AliasMap):

• Forward mapping (original -> alias) – applied to ListTools, ListResources, and ListPrompts responses so clients see the aliased names.
• Reverse mapping (alias -> original) – applied to CallTool, ReadResource, and GetPrompt requests so the backend receives the original name it expects.

Names that have no alias configured pass through unchanged in both directions.

Configuration

Aliases are configured per-backend in TOML. The from field is the backend-local tool name (without the namespace prefix); the to field is the new name to expose:

[[backends]]
name = "files"
transport = "stdio"
command = "file-server"

[[backends.aliases]]
from = "read_file"
to = "read"

[[backends.aliases]]
from = "write_file"
to = "write"

With this config, files/read_file appears to clients as files/read, and calling files/read is transparently forwarded to the backend as files/read_file.

Middleware stack position

Aliasing runs after capability filtering and search-mode filtering, so filters operate on original names and aliases are applied last. The ordering in proxy.rs:

1. Request validation (crate::validation)
2. Capability filtering (crate::filter)
3. Search-mode filtering (crate::filter)
4. Tool aliasing (this module)
5. Composite tools (crate::composite)

Structs

AliasLayer

Tower layer that produces an AliasService.

AliasMap

Resolved alias mappings for all backends.

AliasService

Tower service that rewrites tool names based on alias configuration.