Nexus MCP SDK documentation¶

The groups follow what you came to do: learn the SDK, get a task done, look something up, or understand why the SDK is built this way.

Start here¶

• Getting started: the tutorial. It takes you from an empty directory to a stdio server and a PHP client that calls it.

How-to guides¶

Server¶

• Server API overview: the builder, the lifecycle, and the guide to every feature page.
• Tools: registering tools, structured content, and schema validation.
• Prompts: registering prompt renderers.
• Resources: static and templated resources, and cache hints.
• Completions: serving completion/complete.
• Stores and pagination: page size, custom stores, runtime mutation.
• Custom handlers: vendor-extension methods and spec-method overrides.
• Extensions: enabling SEP-2133 extensions and the capability gate.
• Tasks: brokering tool calls into polled long-running tasks (SEP-2663).
• Apps: declaring ui:// views and linking tools to them (SEP-1865).
• Subscriptions: serving subscriptions/listen streams.
• Asking the client for input: the InputRequiredResult flow.
• Attribute discovery: declaring features with #[AsTool] and friends.

Client¶

• Client API overview: the builder, the lifecycle, and the guide to every feature page.
• Connecting and discovery: attaching a transport and reading server/discover.
• Typed requests: the per-method calls, mirrored tool parameters, and sendRequest().
• When the server asks for input first: answering an InputRequiredResult.
• Progress and timeouts: streaming progress and request deadlines.
• Notification handlers: reacting to server notifications.
• Extensions: enabling SEP-2133 extensions and the outbound gate.
• Tasks: calling tools as tasks and polling them to completion (SEP-2663).
• Apps: advertising renderable mime types and reading _meta.ui (SEP-1865).
• Subscriptions: opening subscriptions/listen streams.

Authorization¶

• Authorization overview: what the SDK enforces and the OAuth error surface.
• Client authorization: composing an authorized client and the user-agent leg.
• Resource server: validating tokens and publishing the metadata document.
• Persisting tokens and registrations: the store interfaces.
• Scopes and step-up: scope selection and insufficient-scope retries.
• OAuth extension grants: client credentials (SEP-1046) and enterprise-managed authorization (SEP-990).
• Provider recipes: Keycloak, Microsoft Entra ID, Auth0, Okta.

Reference¶

• Transports: the transport contract and lifecycle, with one page per binding: stdio, Streamable HTTP, SupervisedTransport, InMemoryTransport.
• Server configuration: everything ServerBuilder takes.
• Client configuration: everything ClientBuilder takes.
• Capability advertisement: how ServerCapabilities is derived.
• ServerContext: what every handler receives.
• Error handling: exception types, JSON-RPC error codes, and the diagnostic message grammar.
• API reference: the generated class-level reference for the public Nexus\Mcp\ API. It tracks the 1.x development branch.

Explanation¶

• Architecture: the namespace tree, layering rules, and the dispatch kernel.
• Spec compliance: coverage against the targeted revision, and the deliberate omissions.
• Design rationale: the choices behind the SDK.
• Best practices: conventions the SDK is shaped to reward.

Runnable code¶

• examples/: demo servers and clients over stdio, in-memory, and HTTP. They include the OAuth and MCP Apps end-to-end setups.