Module mcp 

The parts of MCP that exist as wire headers rather than as IR.

Why this module exists at all

Everything the application layer exchanges is a version-agnostic IR message, and the JSON-RPC envelope around it. A Streamable HTTP request is neither: an HTTP request is addressed by a set of headers, and three of them carry MCP meaning that the IR cannot express — Mcp-Session-Id names the session the request belongs to, and Mcp-Method/Mcp-Name name the operation and the target before a body is even parsed. Those facts are MCP’s, not the IR’s and not the HTTP library’s, so they are value objects here with the rules about what a legal value looks like attached to the type.

This is the first domain/mcp module. It exists because the project rule is that MCP-specific code lives under an mcp submodule in each layer while the protocol-neutral core stays free of MCP types, and putting a header value in domain/ir would have made the IR depend on a transport.

What is deliberately not here

Nothing that reads or writes a header. These types know the grammar of a value and nothing about HTTP: no http::HeaderValue, no request, no status code. The axum adapter in the next stage owns that, and it converts these values at the boundary. A value object that borrowed the HTTP crate’s types would be untestable without an HTTP runtime, and this stage has no HTTP dependency at all by design.

Re-exports

pub use authorization::AuthorizationModel;

pub use authorization::ClientRegistration;

pub use authorization::authorization_model;

pub use resource_metadata::BearerMethod;

pub use resource_metadata::ResourceMetadata;

pub use resource_metadata::ResourceUri;

pub use resource_metadata::ResourceUriError;

pub use resource_metadata::WELL_KNOWN;

Modules

authorization

What each revision’s authorization spec asks of the two sides.

resource_metadata

The canonical resource identifier and the document that publishes it.

Structs

McpSessionId

The Mcp-Session-Id header value naming one session.

RoutingHeaders

A validated Mcp-Method/Mcp-Name pair, proven admissible for one session.

RoutingName

The name of a tool, resource or prompt.

RoutingTarget

The operation a request addresses, and the thing it addresses it against.

Enums

McpSessionIdError

Why a Mcp-Session-Id header is not an McpSessionId.

RoutingHeaderError

Why a request is not routable by header.

Constants

MCP_METHOD_HEADER

The method header’s name, exactly as the specification spells it.

MCP_NAME_HEADER

The target-name header’s name, exactly as the specification spells it.

VISIBLE_ASCII_RANGE

The byte range an Mcp-Session-Id value is drawn from, inclusive.

Functions

client_method_defined_in

Whether method is a client-to-server request version defines.