Crate flymcprust_core 

Runtime and transports for FlyMCPRust.

Most users should depend on the flymcprust facade crate instead.

The core is transport-agnostic: Server turns parsed JSON-RPC messages into responses and implements tower::Service, while transports only move bytes. See docs/ARCHITECTURE.md for the design.

Re-exports

pub use apps::AppUi;

pub use apps::Permission;

pub use apps::Visibility;

pub use auth::Principal;

pub use auth::TokenError;

pub use auth::TokenVerifier;

Modules

apps

MCP Apps (io.modelcontextprotocol/ui): tools that render an interactive HTML interface in the host.

auth

Authorization: the authenticated caller (Principal), access-token verification (TokenVerifier) and scope checks.

jsonrpc

JSON-RPC 2.0 envelope parsing and response serialization.

message

Builders for prompt messages.

security

Helpers for handling untrusted client input safely.

spec

Protocol types of the targeted revision. Protocol types for MCP specification revision 2026-07-28.

testing

In-process test client (feature test-client).

transport

Transports. Each one only moves bytes; all protocol logic lives in Server.

Structs

AutoPrompt

A prompt registered by #[prompt] for automatic discovery.

AutoResource

A resource registered by #[resource] for automatic discovery.

AutoTool

A tool registered by #[tool] for automatic discovery.

Completion

Completion values. Results longer than MAX_COMPLETION_VALUES are truncated, with total and hasMore set accordingly.

CompletionRequest

What the client asked to complete.

Ctx

Context of the request being handled. Declare a Ctx parameter in a tool to receive it; it is excluded from the tool’s input schema.

Json

Wraps a value returned as structured content. The tool’s outputSchema is generated from T, and the result carries both structuredContent and the serialized JSON as text, as the specification recommends.

LegacySession

What a legacy client declared at initialize.

Limits

Resource limits applied to every request.

McpError

A JSON-RPC error returned to the client.

McpRequest

A parsed message plus transport-provided context.

MirroredParam

A tool parameter mirrored into an Mcp-Param-{name} header.

PromptArguments

The arguments of a prompts/get request.

PromptDef

A registered prompt: its protocol description plus its entry point.

ResourceDef

A registered resource or resource template.

Server

A built MCP server. Cheap to clone; all clones share one registry.

ServerBuilder

Builds a Server.

State

Shared application state registered with ServerBuilder::state. Declare a State<T> parameter in a tool to receive it; it is excluded from the tool’s input schema. A tool that needs a state type that was never registered makes ServerBuilder::build fail.

StateRequirement

A shared-state type a handler needs.

ToolDef

A registered tool: its protocol description plus its entry point.

ToolError

An error raised by a tool, resource or prompt handler.

TransportContext

Values attached by the transport to a request (for example, authenticated claims or HTTP headers). Tower middleware can populate it before the request reaches the server.

UriTemplate

A parsed URI template.

UriTemplateError

A template that cannot be parsed or is not supported.

UriVars

Variable values extracted from a URI by UriTemplate::matches.

Enums

BuildError

Errors detected while building a server.

Elicitation

The outcome of an elicitation.

ErrorKind

How an error relates to the request, independent of transport. HTTP uses it to pick a status code (400, 404, 200 or 500).

ParamKind

JSON Schema primitive type of a mirrored parameter.

ToolOutput

What a tool produced.

Constants

LEGACY_PROTOCOL_VERSIONS

Legacy protocol versions the server accepts, newest first.

MAX_COMPLETION_VALUES

Maximum number of values in one completion result (specification limit).

MAX_SUPPORTED_JSON_DEPTH

Hard upper bound for Limits::max_json_depth: serde_json refuses to nest deeper than this regardless of configuration.

MIN_REQUEST_STATE_KEY_BYTES

Minimum length of a requestState signing key.

Traits

Extension

A protocol extension supported by the server.

IntoContent

Content that can appear in a message: &str, String (as text) and the specification’s content types.

IntoPromptResult

Conversion of a prompt’s return value into a result.

IntoResourceContents

Conversion of a resource handler’s return value into contents.

IntoToolError

Conversion of tool errors. Implemented for ToolError and for every std::error::Error (treated as internal).

IntoToolResult

Conversion of a tool’s return value into a result.

Prompt

A prompt that can be registered with ServerBuilder::prompt.

Resource

A resource that can be registered with ServerBuilder::resource.

Tool

A tool that can be registered with ServerBuilder::tool.

Functions

input_schema_for

Builds a tool inputSchema from the JSON Schema of T, which must describe an object (tool arguments are always a JSON object).

is_legacy_version

Whether a protocol version is one of the supported legacy versions.

output_schema_from

Wraps a generated schema as a tool outputSchema.

parse_arguments

Deserializes tool arguments. A missing arguments member is treated as an empty object.

parse_optional_uri_var

Like parse_uri_var for optional (query) variables.

parse_uri_var

Parses a template variable for a resource handler. A value that does not parse means no such resource exists.

schema_for

Generates a JSON Schema (2020-12) for T, as used in inputSchema and outputSchema. The root $schema and title keys are removed: 2020-12 is the default dialect, and the title would expose a Rust type name.

Type Aliases

CallFn

Entry point of a tool: deserializes the arguments synchronously (borrowing the request buffer) and returns the future that runs the tool.

CompleteFn

A completion provider. Completion runs synchronously and must be fast.

GetFn

Entry point of a prompt: receives the (string) arguments of prompts/get.

PromptFuture

The future returned by a prompt.

ReadFn

Entry point of a resource: receives the requested URI and, for templates, the variables extracted from it.

ResourceContents

One item of a resources/read result.

ResourceFuture

The future returned by a resource read.

ToolFuture

The future returned by a tool invocation.

ToolResult

The outcome of a tool invocation.