115 pages for initialize.

Architecture overview Model Context Protocol · in the page docs/2025-03-26/learn/architecture …ycle management](#lifecycle-management) section, the client sends an `initialize` request to establish the connection and negotiate supported features. ```json Initialize Request theme={null} { "js… Debugging Model Context Protocol · in the page docs/2025-03-26/tools/debugging …to a client that hasn't declared that capability. Inspect the [`initialize` exchange](/specification/2025-03-26/basic/lifecycle#initialization) to verify both sides declared what you expect… Understanding Authorization in MCP Model Context Protocol · in the page docs/2025-03-26/tutorials/security/authorization …from "@modelcontextprotocol/sdk/server/streamableHttp.js"; import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js"; import { z } from "zod"; import cors from "cors"; import { mcpAut… Security Best Practices Model Context Protocol · in the page docs/2025-03-26/tutorials/security/security_best_practices …participant ServerB participant Attacker Client->>ServerA: Initialize (connect to streamable HTTP server) ServerA-->>Client: Respond with session ID Attacker->>ServerB: Access/gues… Build an MCP client Model Context Protocol · in the page docs/2025-06-18/develop/build-client …riables from .env class MCPClient: def __init__(self): # Initialize session and client objects self.session: Optional[ClientSession] = None self.exit_stack = AsyncExitStac… Build an MCP server Model Context Protocol · in the page docs/2025-06-18/develop/build-server …ng import Any import httpx from mcp.server.fastmcp import FastMCP # Initialize FastMCP server mcp = FastMCP("weather") # Constants NWS_API_BASE = "https://api.weather.gov" USER_AGENT = "weather-app… Client Best Practices Model Context Protocol · in the page docs/2025-06-18/develop/clients/client-best-practices …ble Model->>Host: enable_server("salesforce") Host->>Server: Initialize connection Server-->>Host: Server capabilities + tools Host-->>Model: Salesforce server connected Note ove… Architecture overview Model Context Protocol · in the page docs/2025-06-18/learn/architecture …ycle management](#lifecycle-management) section, the client sends an `initialize` request to establish the connection and negotiate supported features. ```json Initialize Request theme={null} { "js… Debugging Model Context Protocol · in the page docs/2025-06-18/tools/debugging …to a client that hasn't declared that capability. Inspect the [`initialize` exchange](/specification/2025-06-18/basic/lifecycle#initialization) to verify both sides declared what you expect… Understanding Authorization in MCP Model Context Protocol · in the page docs/2025-06-18/tutorials/security/authorization …from "@modelcontextprotocol/sdk/server/streamableHttp.js"; import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js"; import { z } from "zod"; import cors from "cors"; import { mcpAut… Security Best Practices Model Context Protocol · in the page docs/2025-06-18/tutorials/security/security_best_practices …participant ServerB participant Attacker Client->>ServerA: Initialize (connect to streamable HTTP server) ServerA-->>Client: Respond with session ID Attacker->>ServerB: Access/gues… Build an MCP client Model Context Protocol · in the page docs/2025-11-25/develop/build-client …riables from .env class MCPClient: def __init__(self): # Initialize session and client objects self.session: Optional[ClientSession] = None self.exit_stack = AsyncExitStac… Build an MCP server Model Context Protocol · in the page docs/2025-11-25/develop/build-server …ng import Any import httpx from mcp.server.fastmcp import FastMCP # Initialize FastMCP server mcp = FastMCP("weather") # Constants NWS_API_BASE = "https://api.weather.gov" USER_AGENT = "weather-app… Client Best Practices Model Context Protocol · in the page docs/2025-11-25/develop/clients/client-best-practices …ble Model->>Host: enable_server("salesforce") Host->>Server: Initialize connection Server-->>Host: Server capabilities + tools Host-->>Model: Salesforce server connected Note ove… Architecture overview Model Context Protocol · in the page docs/2025-11-25/learn/architecture …ycle management](#lifecycle-management) section, the client sends an `initialize` request to establish the connection and negotiate supported features. ```json Initialize Request theme={null} { "js… Debugging Model Context Protocol · in the page docs/2025-11-25/tools/debugging …to a client that hasn't declared that capability. Inspect the [`initialize` exchange](/specification/2025-11-25/basic/lifecycle#initialization) to verify both sides declared what you expect… Understanding Authorization in MCP Model Context Protocol · in the page docs/2025-11-25/tutorials/security/authorization …from "@modelcontextprotocol/sdk/server/streamableHttp.js"; import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js"; import { z } from "zod"; import cors from "cors"; import { mcpAut… Security Best Practices Model Context Protocol · in the page docs/2025-11-25/tutorials/security/security_best_practices …participant ServerB participant Attacker Client->>ServerA: Initialize (connect to streamable HTTP server) ServerA-->>Client: Respond with session ID Attacker->>ServerB: Access/gues… Build an MCP client Model Context Protocol · in the page docs/2026-07-28/develop/build-client …seconds to return * This is normal and happens while: * The server initializes * Claude processes the query * Tools are being executed * Subsequent responses are typically faster * Don't interr… Build an MCP server Model Context Protocol · in the page docs/2026-07-28/develop/build-server …typing import Any import httpx2 from mcp.server import MCPServer # Initialize MCPServer mcp = MCPServer("weather") # Constants NWS_API_BASE = "https://api.weather.gov" USER_AGENT = "weather-app/1.… CLI client Model Context Protocol · in the page docs/2026-07-28/tools/inspector/cli …ethods | `--method` | Required companions | Notes | | - | - | - | | `initialize` | None | Connect-only probe: `{serverInfo, protocolVersion, capabilities, instructions}`. | | `tools/list` | None | `-… Protocol eras Model Context Protocol · in the page docs/2026-07-28/tools/inspector/protocol-eras …ctor does at connect | | - | - | | `legacy` | **The default.** Plain `initialize`, no probing at all. | | `auto` | Probe `server/discover` first, and fall back to `initialize` on any non-modern outcom… Recipes Model Context Protocol · in the page docs/2026-07-28/tools/inspector/recipes …apps ``` `--advertise-apps` makes the CLI claim MCP Apps support at `initialize`. It is off by default because the CLI cannot render an app, but a server that shows its app tools only to app-capable… Understanding Authorization in MCP Model Context Protocol · in the page docs/2026-07-28/tutorials/security/authorization …from "@modelcontextprotocol/sdk/server/streamableHttp.js"; import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js"; import { z } from "zod"; import cors from "cors"; import { mcpAut… Build an MCP client Model Context Protocol · in the page docs/draft/develop/build-client …seconds to return * This is normal and happens while: * The server initializes * Claude processes the query * Tools are being executed * Subsequent responses are typically faster * Don't interr… Build an MCP server Model Context Protocol · in the page docs/draft/develop/build-server …typing import Any import httpx2 from mcp.server import MCPServer # Initialize MCPServer mcp = MCPServer("weather") # Constants NWS_API_BASE = "https://api.weather.gov" USER_AGENT = "weather-app/1.… CLI client Model Context Protocol · in the page docs/draft/tools/inspector/cli …ethods | `--method` | Required companions | Notes | | - | - | - | | `initialize` | None | Connect-only probe: `{serverInfo, protocolVersion, capabilities, instructions}`. | | `tools/list` | None | `-… Protocol eras Model Context Protocol · in the page docs/draft/tools/inspector/protocol-eras …ctor does at connect | | - | - | | `legacy` | **The default.** Plain `initialize`, no probing at all. | | `auto` | Probe `server/discover` first, and fall back to `initialize` on any non-modern outcom… Recipes Model Context Protocol · in the page docs/draft/tools/inspector/recipes …apps ``` `--advertise-apps` makes the CLI claim MCP Apps support at `initialize`. It is off by default because the CLI cannot render an app, but a server that shows its app tools only to app-capable… Understanding Authorization in MCP Model Context Protocol · in the page docs/draft/tutorials/security/authorization …from "@modelcontextprotocol/sdk/server/streamableHttp.js"; import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js"; import { z } from "zod"; import cors from "cors"; import { mcpAut… Build an MCP App Model Context Protocol · in the page extensions/apps/build …tablishes communication with the host. Call this once when your app initializes. * **`app.ontoolresult`**: A callback that fires when the host pushes a tool result to your app (e.g., when the tool… MCP Apps Model Context Protocol · in the page extensions/apps/overview …ore MCP protocol (e.g., `tools/call`), some are similar (e.g., `ui/initialize`), and most are new with a `ui/` method name prefix. The app can request tool calls, send messages, update the model… SEP-2133: Extensions Model Context Protocol · in the page seps/2133-extensions …#### Client Capabilities Clients advertise extension support in the `initialize` request: ```json theme={null} { "jsonrpc": "2.0", "id": 1, "method": "initialize", "params": { "protocolV… SEP-2243: HTTP Header Standardization for Streamable HTTP Transport Model Context Protocol · in the page seps/2243-http-standardization …={null} POST /mcp HTTP/1.1 Content-Type: application/json Mcp-Method: initialize { "jsonrpc": "2.0", "id": 4, "method": "initialize", "params": { "protocolVersion": "2025-06-18", "cap… SEP-2322: Multi Round-Trip Requests Model Context Protocol · in the page seps/2322-MRTR …| InputRequiredResult Supported | | - | - | | `PingRequest` | No | | `InitializeRequest` | No | | `CompleteRequest` | No | | `SetLevelRequest` | No | | `ListPromptsRequest` | No | | `ListResourcesRequ… SEP-2567: Sessionless MCP via Explicit State Handles Model Context Protocol · in the page seps/2567-sessionless-mcp …carries and threads through subsequent calls. [SEP-2575] removes the `initialize` handshake and carries protocol version and capabilities per-request; this proposal is the complementary change that re… SEP-2575: Make MCP Stateless Model Context Protocol · in the page seps/2575-stateless-mcp …ilities, the following RPC methods and notifications are removed: * `initialize` / `notifications/initialized`: The initialization handshake is removed. Version negotiation is handled per-request v… Architecture Model Context Protocol · in the page specification/2024-11-05/architecture/index …st participant Client participant Server Host->>+Client: Initialize client Client->>+Server: Initialize session with capabilities Server-->>Client: Respond with supported capabili… Lifecycle Model Context Protocol · in the page specification/2024-11-05/basic/lifecycle …erver: Initialization Phase activate Client Client->>+Server: initialize request Server-->>Client: initialize response Client--)Server: initialized notification Note over Client,S… Cancellation Model Context Protocol · in the page specification/2024-11-05/basic/utilities/cancellation …the same direction * Are believed to still be in-progress 2. The `initialize` request **MUST NOT** be cancelled by clients 3. Receivers of cancellation notifications **SHOULD**: * Stop processi… Architecture Model Context Protocol · in the page specification/2025-03-26/architecture/index …st participant Client participant Server Host->>+Client: Initialize client Client->>+Server: Initialize session with capabilities Server-->>Client: Respond with supported capabili… Lifecycle Model Context Protocol · in the page specification/2025-03-26/basic/lifecycle …erver: Initialization Phase activate Client Client->>+Server: initialize request Server-->>Client: initialize response Client--)Server: initialized notification Note over Client,S… Transports Model Context Protocol · in the page specification/2025-03-26/basic/transports …in an `Mcp-Session-Id` header on the HTTP response containing the `InitializeResult`. * The session ID **SHOULD** be globally unique and cryptographically secure (e.g., a securely generated… Cancellation Model Context Protocol · in the page specification/2025-03-26/basic/utilities/cancellation …the same direction * Are believed to still be in-progress 2. The `initialize` request **MUST NOT** be cancelled by clients 3. Receivers of cancellation notifications **SHOULD**: * Stop processi… Architecture Model Context Protocol · in the page specification/2025-06-18/architecture/index …st participant Client participant Server Host->>+Client: Initialize client Client->>+Server: Initialize session with capabilities Server-->>Client: Respond with supported capabili… Lifecycle Model Context Protocol · in the page specification/2025-06-18/basic/lifecycle …erver: Initialization Phase activate Client Client->>+Server: initialize request Server-->>Client: initialize response Client--)Server: initialized notification Note over Client,S… Transports Model Context Protocol · in the page specification/2025-06-18/basic/transports …in an `Mcp-Session-Id` header on the HTTP response containing the `InitializeResult`. * The session ID **SHOULD** be globally unique and cryptographically secure (e.g., a securely generated… Cancellation Model Context Protocol · in the page specification/2025-06-18/basic/utilities/cancellation …the same direction * Are believed to still be in-progress 2. The `initialize` request **MUST NOT** be cancelled by clients 3. Receivers of cancellation notifications **SHOULD**: * Stop processi… Schema Reference Model Context Protocol · in the page specification/2025-06-18/schema …sets/icons.svg#icon-anchor" /></svg></a></div> </section> </div> ## `initialize` <div class="type"> ### `InitializeRequest` <div class="tsd-signature"><span class="tsd-signature-keyword">interf… Architecture Model Context Protocol · in the page specification/2025-11-25/architecture/index …st participant Client participant Server Host->>+Client: Initialize client Client->>+Server: Initialize session with capabilities Server-->>Client: Respond with supported capabili…