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Releases

@modelcontextprotocol/client@2.5.0

Minor Changes

• #3115 1e608ca Thanks @mattzcarey! - Client, Server and McpServer now emit OpenTelemetry spans and mcp.client.operation.duration / mcp.server.operation.duration histograms for every MCP request and notification except notifications/message, following the OpenTelemetry semantic conventions for MCP, and propagate W3C trace context through params._meta (SEP-414). There is nothing to configure: register an OpenTelemetry SDK and MCP traffic shows up. Pass openTelemetry: false to a Client, Server or McpServer to turn its instrumentation off. Without one, the OpenTelemetry API is a no-op, nothing is recorded and messages are unchanged.

  @opentelemetry/api (^1.9.0) is a new required peer dependency of @modelcontextprotocol/client and @modelcontextprotocol/server, so the SDK uses the same copy as the application's OpenTelemetry SDK. npm 7+, pnpm 8+ and Bun install it automatically. Setups that don't install peers must add @opentelemetry/api to their dependencies, or importing either package fails: Yarn (classic, and Berry with any linker), npm --legacy-peer-deps, and pnpm with auto-install-peers=false.

  What changes for applications that already run an OpenTelemetry SDK:

  • MCP spans and metrics appear under the @modelcontextprotocol/client and @modelcontextprotocol/server instrumentation scopes. If you already trace MCP, pass openTelemetry: false, or with Sentry remove its McpServer integration, to avoid duplicate spans. Filtering the MCP scopes instead leaves handler spans parented on spans that are never exported.
  • Outgoing requests and notifications carry whatever your global propagator writes, in params._meta, as HTTP requests carry it in headers: traceparent and tracestate, plus baggage if the propagator includes W3C Baggage (the NodeSDK default), so baggage entries reach MCP peers, including third-party servers. Register W3CTraceContextPropagator alone to send trace context only.
  • Servers that validate a custom method's params with a strict schema need an optional _meta member, as they already do for callers that pass onprogress.

  Spans do not record tool arguments, tool results or prompt arguments. They do record JSON-RPC error messages, handler exception messages and resource URIs. The span and attribute names are experimental while the MCP semantic conventions are in development.

Patch Changes

• #3108 39ae8e6 Thanks @claude! - The bundled Ajv validator is now built with fast-uri 3.1.9 (was 3.1.8). A schema no longer compiles when a $id or $ref has a percent-encoded character before its first colon (%61:b), or { or } in the host of an http, https, ws or wss URL (http://{host}/a). Relative values keep their leading .. segments: a $ref to a $id such as ../a now resolves, and a $ref of only dot segments (., ../) no longer resolves to the root schema. Plain names, #/$defs/... references, other URLs and URNs are not affected.

• #2877 b415e60 Thanks @dasjideepak! - Add OAuthClientProvider.skipOfflineAccessConsentPrompt (and the matching startAuthorization() option) so a client can omit the prompt=consent the SDK adds when the requested scope includes offline_access. Default behavior is unchanged. This unblocks authorization servers such as Microsoft Entra ID tenants that have user consent disabled and admin consent granted, where a forced consent prompt fails with AADSTS90095 for non-admin users.

• Updated dependencies []:

  • @modelcontextprotocol/core@2.5.0

@modelcontextprotocol/server@2.5.0

Minor Changes

• #3115 1e608ca Thanks @mattzcarey! - Client, Server and McpServer now emit OpenTelemetry spans and mcp.client.operation.duration / mcp.server.operation.duration histograms for every MCP request and notification except notifications/message, following the OpenTelemetry semantic conventions for MCP, and propagate W3C trace context through params._meta (SEP-414). There is nothing to configure: register an OpenTelemetry SDK and MCP traffic shows up. Pass openTelemetry: false to a Client, Server or McpServer to turn its instrumentation off. Without one, the OpenTelemetry API is a no-op, nothing is recorded and messages are unchanged.

  @opentelemetry/api (^1.9.0) is a new required peer dependency of @modelcontextprotocol/client and @modelcontextprotocol/server, so the SDK uses the same copy as the application's OpenTelemetry SDK. npm 7+, pnpm 8+ and Bun install it automatically. Setups that don't install peers must add @opentelemetry/api to their dependencies, or importing either package fails: Yarn (classic, and Berry with any linker), npm --legacy-peer-deps, and pnpm with auto-install-peers=false.

  What changes for applications that already run an OpenTelemetry SDK:

  • MCP spans and metrics appear under the @modelcontextprotocol/client and @modelcontextprotocol/server instrumentation scopes. If you already trace MCP, pass openTelemetry: false, or with Sentry remove its McpServer integration, to avoid duplicate spans. Filtering the MCP scopes instead leaves handler spans parented on spans that are never exported.
  • Outgoing requests and notifications carry whatever your global propagator writes, in params._meta, as HTTP requests carry it in headers: traceparent and tracestate, plus baggage if the propagator includes W3C Baggage (the NodeSDK default), so baggage entries reach MCP peers, including third-party servers. Register W3CTraceContextPropagator alone to send trace context only.
  • Servers that validate a custom method's params with a strict schema need an optional _meta member, as they already do for callers that pass onprogress.

  Spans do not record tool arguments, tool results or prompt arguments. They do record JSON-RPC error messages, handler exception messages and resource URIs. The span and attribute names are experimental while the MCP semantic conventions are in development.

Patch Changes

• #3108 39ae8e6 Thanks @claude! - The bundled Ajv validator is now built with fast-uri 3.1.9 (was 3.1.8). A schema no longer compiles when a $id or $ref has a percent-encoded character before its first colon (%61:b), or { or } in the host of an http, https, ws or wss URL (http://{host}/a). Relative values keep their leading .. segments: a $ref to a $id such as ../a now resolves, and a $ref of only dot segments (., ../) no longer resolves to the root schema. Plain names, #/$defs/... references, other URLs and URNs are not affected.

• Updated dependencies []:

  • @modelcontextprotocol/core@2.5.0

@modelcontextprotocol/server-legacy@2.5.0

Patch Changes

• Updated dependencies []:
  • @modelcontextprotocol/core@2.5.0

@modelcontextprotocol/codemod@2.5.0

@modelcontextprotocol/core@2.5.0

@modelcontextprotocol/core-internal@2.1.0

Minor Changes

• #3115 1e608ca Thanks @mattzcarey! - Client, Server and McpServer now emit OpenTelemetry spans and mcp.client.operation.duration / mcp.server.operation.duration histograms for every MCP request and notification except notifications/message, following the OpenTelemetry semantic conventions for MCP, and propagate W3C trace context through params._meta (SEP-414). There is nothing to configure: register an OpenTelemetry SDK and MCP traffic shows up. Pass openTelemetry: false to a Client, Server or McpServer to turn its instrumentation off. Without one, the OpenTelemetry API is a no-op, nothing is recorded and messages are unchanged.

  @opentelemetry/api (^1.9.0) is a new required peer dependency of @modelcontextprotocol/client and @modelcontextprotocol/server, so the SDK uses the same copy as the application's OpenTelemetry SDK. npm 7+, pnpm 8+ and Bun install it automatically. Setups that don't install peers must add @opentelemetry/api to their dependencies, or importing either package fails: Yarn (classic, and Berry with any linker), npm --legacy-peer-deps, and pnpm with auto-install-peers=false.

  What changes for applications that already run an OpenTelemetry SDK:

  • MCP spans and metrics appear under the @modelcontextprotocol/client and @modelcontextprotocol/server instrumentation scopes. If you already trace MCP, pass openTelemetry: false, or with Sentry remove its McpServer integration, to avoid duplicate spans. Filtering the MCP scopes instead leaves handler spans parented on spans that are never exported.
  • Outgoing requests and notifications carry whatever your global propagator writes, in params._meta, as HTTP requests carry it in headers: traceparent and tracestate, plus baggage if the propagator includes W3C Baggage (the NodeSDK default), so baggage entries reach MCP peers, including third-party servers. Register W3CTraceContextPropagator alone to send trace context only.
  • Servers that validate a custom method's params with a strict schema need an optional _meta member, as they already do for callers that pass onprogress.

  Spans do not record tool arguments, tool results or prompt arguments. They do record JSON-RPC error messages, handler exception messages and resource URIs. The span and attribute names are experimental while the MCP semantic conventions are in development.

Patch Changes

• Updated dependencies []:
  • @modelcontextprotocol/core@2.5.0