Module wire 

MCP wire types — the Model Context Protocol message surface, shared by the client and the served-MCP side.

Method/notification names are constants (typos become compile errors). Result/param structs use camelCase to match the spec. content[] and resource contents[] are kept as Vec<Value> with text-extraction helpers rather than a brittle tagged enum, so an unknown content type from a newer server is preserved, not a parse error (forward-compat).

The protocol version + era model lives in crate::version; it is re-exported here so mcp::wire::{PROTOCOL_VERSION, negotiate_version, …} resolves.

Re-exports

pub use crate::version::*;

Modules

method

Method + notification names. Constants, so a typo is a compile error rather than a -32601 at runtime.

Structs

CallToolParams

CallToolResult

Result of tools/call. is_error: true is a tool-domain failure (fed to the model as an observation so it can adapt), distinct from a JSON-RPC transport error, which fails the call outright.

ClientCapabilities

Capabilities a client declares. Only declare what the client can actually service: a server is entitled to call anything advertised here, and a declared-but-unanswerable capability strands it waiting on a reply.

CompleteParams

completion/complete params: what to complete (a ref to a prompt or resource template) and the argument being typed. Kept as Value — the ref shape varies by target and revision (forward-compat).

CompleteResult

Completion

DiscoverResult

Result of server/discover (modern era): the server’s supported protocol versions, capabilities, and identity in a single call — the stateless replacement for the legacy initialize capability exchange. resultType and the caching fields (ttlMs/cacheScope) are carried for forward-compat.

GetPromptParams

prompts/get params — the template name + its argument fills (all strings).

GetPromptResult

prompts/get result — the rendered messages. messages[] is kept as Vec<Value> (each {role, content}) for forward-compat with content types.

Implementation

InitializeParams

InitializeResult

ListPromptsResult

ListResourceTemplatesResult

ListResourcesResult

ListToolsResult

Prompt

A prompt template a server offers via prompts/list. arguments describe the template’s fill-ins.

PromptArgument

ReadResourceParams

ReadResourceResult

Resource

ResourceTemplate

A resource template (a parameterized uriTemplate, RFC 6570) a server offers via resources/templates/list — distinct from a concrete Resource.

ResourceUpdatedParams

Payload of notifications/resources/updated — URI only, never a diff. The notification is a wake-up, not the data: the reader re-reads the URI on wake, so a burst of updates collapses into one read of the current state and a missed notification costs freshness, not correctness.

ResourcesCapability

ServerCapabilities

What a server says it can do. Every call is gated on these, and the gate is fail-closed — an absent capability is a refusal, not a maybe: no tools/call unless tools is present; no resources/subscribe unless resources.subscribe == Some(true).

SubscribeParams

resources/subscribe / resources/unsubscribe params. Per-URI only: a subscription names one concrete resource, never a ResourceTemplate, since a template matches an open-ended set with no item to watch.

Task

A durable async-task handle (the tasks extension). A supported request (e.g. tools/call) may return one (resultType: "task") instead of blocking; the client polls method::TASKS_GET until a terminal status.

Tool

ToolsCapability

Constants

TASKS_EXTENSION

The tasks extension identifier — advertised in capabilities.extensions to opt into task-augmented (async long-running) requests.

Functions

as_task_result

If a result value is a task handle (resultType: "task"), parse it — the polymorphic shape a task-augmented request returns instead of its normal result.