--- title: "MCP Monitoring" description: "Monitor MCP server tool executions, prompt retrievals, resource access, and errors." url: https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring/ --- # Set Up MCP Monitoring | Sentry for Cloudflare With Sentry's [MCP Monitoring](https://docs.sentry.io/product/mcp-servers.md), you can track and debug MCP servers with full-stack context. You can monitor tool executions, prompt retrievals, resource access, and error rates alongside your other Sentry data, including logs, errors, and traces. Before you begin, [set up tracing](https://docs.sentry.io/platforms/javascript/guides/cloudflare/tracing.md). ## [Instrument the MCP Server](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#instrument-the-mcp-server) Wrap each `McpServer` instance with `wrapMcpServerWithSentry` to automatically record MCP requests, tool calls, prompt retrievals, resource reads, and handler errors. Import Sentry from your framework's SDK package, then wrap the MCP server instance before connecting it to a transport: ```javascript import * as Sentry from ""; import { McpServer } from "@modelcontextprotocol/server"; const server = Sentry.wrapMcpServerWithSentry( new McpServer({ name: "my-mcp-server", version: "1.0.0", }), ); ``` Register tools, prompts, and resources on `server` as usual. The wrapper returns the same server instance. Support for `@modelcontextprotocol/server` 2.x requires Sentry JavaScript SDK version `10.70.0` or newer. For `@modelcontextprotocol/sdk` 1.x, use Sentry JavaScript SDK version `9.46.0` or newer and import `McpServer` from `@modelcontextprotocol/sdk/server/mcp.js`. The Sentry wrapper is otherwise the same. ### [Configure Input and Output Recording](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#configure-input-and-output-recording) MCP inputs and outputs may contain sensitive data. Use `recordInputs` and `recordOutputs` to control collection for a specific server: ```javascript const server = Sentry.wrapMcpServerWithSentry(mcpServer, { recordInputs: false, recordOutputs: false, }); ``` These options override the corresponding `dataCollection.genAI.inputs` and `dataCollection.genAI.outputs` settings and require Sentry JavaScript SDK version `10.33.0` or newer. ## [Preserve MCP Spans After the Response](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#preserve-mcp-spans-after-the-response) Cloudflare MCP work can finish after the Worker returns an HTTP response, including work kept alive with `waitUntil()`. With the static trace lifecycle, Sentry snapshots the request transaction when the response is returned, so MCP spans that finish later may be missing. Set `traceLifecycle: "stream"` so the SDK can send each sampled span when it finishes. This changes how spans are delivered; you still need to wrap the MCP server as shown above. Span streaming on Cloudflare requires `@sentry/cloudflare` version `10.49.0` or newer. ```javascript import * as Sentry from "@sentry/cloudflare"; const worker = { async fetch(request, env, ctx) { return handleMcpRequest(request, env, ctx); }, }; export default Sentry.withSentry( (env) => ({ dsn: env.SENTRY_DSN, tracesSampleRate: 1.0, traceLifecycle: "stream", }), worker, ); ``` Stream mode sends span records instead of assembling one transaction event with embedded spans. `beforeSendTransaction` and `ignoreTransactions` don't apply to streamed spans. See [Streamed Spans](https://docs.sentry.io/platforms/javascript/guides/cloudflare/tracing/streamed-spans.md) for the `beforeSendSpan` and `ignoreSpans` configuration. If you use `McpAgent`, wrap the `McpServer` returned by its `server` getter, and wrap the Agent class separately with `instrumentAgentWithSentry` to preserve request and RPC context. Agent instrumentation, MCP server wrapping, and span streaming solve different parts of the setup; none replaces the others. See [Agents SDK](https://docs.sentry.io/platforms/javascript/guides/cloudflare/features/agents-sdk.md). ## [Manual Instrumentation](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#manual-instrumentation) The setup above automatically instruments MCP servers built with the official [MCP SDK](https://github.com/modelcontextprotocol/typescript-sdk) (`@modelcontextprotocol/sdk`). If your server uses a different library or a custom implementation that `wrapMcpServerWithSentry` can't wrap, you can record the same spans manually. You don't need this if you're already using `wrapMcpServerWithSentry` — it creates these spans for you. Otherwise, use [Sentry.startSpan()](https://docs.sentry.io/platforms/javascript/tracing/instrumentation/custom-instrumentation.md#starting-a-span) to create the spans described below. ## [Spans](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#spans) ### [Tool Execution Span](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#tool-execution-span) Describes MCP tool execution. * The span `op` (transaction mode) or the span's `sentry.op` attribute (stream mode) MUST be `"mcp.server"`. * The span `name` SHOULD be `"tools/call {mcp.tool.name}"`. * The `mcp.tool.name` attribute MUST be set to the tool's name. (e.g. `"get_weather"`) * The `mcp.method.name` attribute SHOULD be set to `"tools/call"`. * All [Common Span Attributes](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#common-span-attributes) SHOULD be set. Additional attributes on the span: | Data Attribute | Type | Requirement Level | Description | Example | | ------------------------------- | ------- | ----------------- | -------------------------------------------------------- | ------------------------------------------------- | | `mcp.tool.name` | string | required | The name of the MCP tool being called. | `"get_weather"` | | `mcp.method.name` | string | recommended | Should be set to "tools/call". | `"tools/call"` | | `mcp.request.id` | string | optional | The unique identifier for the MCP request. | `"req_123abc"` | | `mcp.request.argument.*` | any | optional | Tool input arguments (requires `send_default_pii=True`). | `"San Francisco"` for `mcp.request.argument.city` | | `mcp.tool.result.content` | string | optional | The result/output content from the tool execution. | `"The weather is sunny"` | | `mcp.tool.result.content_count` | int | optional | The number of items/keys in the tool result. | `5` | | `mcp.tool.result.is_error` | boolean | optional | Whether the tool execution resulted in an error. | `True` | #### [Example Tool Execution Span:](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#example-tool-execution-span) ```javascript // Example tool execution const toolName = "get_weather"; const toolArguments = { city: "San Francisco" }; await Sentry.startSpan( { op: "mcp.server", name: `tools/call ${toolName}`, }, async (span) => { // Set MCP-specific attributes span.setAttribute("mcp.tool.name", toolName); span.setAttribute("mcp.method.name", "tools/call"); // Set request metadata span.setAttribute("mcp.request.id", "req_123abc"); span.setAttribute("mcp.session.id", "session_xyz789"); span.setAttribute("mcp.transport", "stdio"); // or "http", "sse" for HTTP/WebSocket/SSE span.setAttribute("network.transport", "pipe"); // or "tcp" for HTTP/SSE // Set tool arguments (optional, requires recordInputs: true) for (const [key, value] of Object.entries(toolArguments)) { span.setAttribute(`mcp.request.argument.${key}`, value); } // Execute the tool try { const result = executeTool(toolName, toolArguments); // Set result data span.setAttribute("mcp.tool.result.content", JSON.stringify(result)); span.setAttribute("mcp.tool.result.is_error", false); // Set result content count if applicable if ( Array.isArray(result) || (typeof result === "object" && result !== null) ) { span.setAttribute( "mcp.tool.result.content_count", Array.isArray(result) ? result.length : Object.keys(result).length, ); } } catch (error) { span.setAttribute("mcp.tool.result.is_error", true); throw error; } }, ); ``` ### [Prompt Retrieval Span](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#prompt-retrieval-span) Describes MCP prompt retrieval. * The span `op` (transaction mode) or the span's `sentry.op` attribute (stream mode) MUST be `"mcp.server"`. * The span `name` SHOULD be `"prompts/get {mcp.prompt.name}"`. * The `mcp.prompt.name` attribute MUST be set to the prompt's name. (e.g. `"code_review"`) * The `mcp.method.name` attribute SHOULD be set to `"prompts/get"`. * All [Common Span Attributes](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#common-span-attributes) SHOULD be set. Additional attributes on the span: | Data Attribute | Type | Requirement Level | Description | Example | | ----------------------------------- | ------ | ----------------- | --------------------------------------------------------------------------------- | ---------------------------------------------- | | `mcp.prompt.name` | string | required | The name of the MCP prompt being retrieved. | `"code_review"` | | `mcp.method.name` | string | recommended | Should be set to "prompts/get". | `"prompts/get"` | | `mcp.request.id` | string | optional | The unique identifier for the MCP request. | `"req_456def"` | | `mcp.request.argument.*` | any | optional | Prompt input arguments (requires `send_default_pii=True`). | `"python"` for `mcp.request.argument.language` | | `mcp.prompt.result.message_content` | string | optional | The message content from the prompt retrieval (requires `send_default_pii=True`). | `"Review the following code..."` | | `mcp.prompt.result.message_role` | string | optional | The role of the message (only for single-message prompts). | `"user"`, `"assistant"`, `"system"` | | `mcp.prompt.result.message_count` | int | optional | The number of messages in the prompt result. | `1`, `3` | #### [Example Prompt Retrieval Span:](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#example-prompt-retrieval-span) ```javascript // Example prompt retrieval const promptName = "code_review"; const promptArguments = { language: "python" }; await Sentry.startSpan( { op: "mcp.server", name: `prompts/get ${promptName}`, }, async (span) => { // Set MCP-specific attributes span.setAttribute("mcp.prompt.name", promptName); span.setAttribute("mcp.method.name", "prompts/get"); // Set request metadata span.setAttribute("mcp.request.id", "req_456def"); span.setAttribute("mcp.session.id", "session_xyz789"); span.setAttribute("mcp.transport", "http"); span.setAttribute("network.transport", "tcp"); // Set prompt arguments (optional, requires recordInputs: true) for (const [key, value] of Object.entries(promptArguments)) { span.setAttribute(`mcp.request.argument.${key}`, value); } // Retrieve the prompt const promptResult = getPrompt(promptName, promptArguments); // Set result data const messages = promptResult.messages || []; span.setAttribute("mcp.prompt.result.message_count", messages.length); // For single-message prompts, set role and content if (messages.length === 1) { span.setAttribute( "mcp.prompt.result.message_role", messages[0].role, ); // Content may contain sensitive data, only set if recordOutputs: true span.setAttribute( "mcp.prompt.result.message_content", JSON.stringify(messages[0].content), ); } }, ); ``` ### [Resource Read Span](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#resource-read-span) Describes MCP resource access. * The span `op` (transaction mode) or the span's `sentry.op` attribute (stream mode) MUST be `"mcp.server"`. * The span `name` SHOULD be `"resources/read {mcp.resource.uri}"`. * The `mcp.resource.uri` attribute MUST be set to the resource's URI. (e.g. `"file:///path/to/resource"`) * The `mcp.method.name` attribute SHOULD be set to `"resources/read"`. * All [Common Span Attributes](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#common-span-attributes) SHOULD be set. Additional attributes on the span: | Data Attribute | Type | Requirement Level | Description | Example | | ----------------------- | ------ | ----------------- | -------------------------------------------- | ----------------------------- | | `mcp.resource.uri` | string | required | The URI of the MCP resource being accessed. | `"file:///path/to/resource"` | | `mcp.method.name` | string | recommended | Should be set to "resources/read" | `"resources/read"` | | `mcp.request.id` | string | optional | The unique identifier for the MCP request. | `"req_789ghi"` | | `mcp.resource.protocol` | string | optional | The protocol/scheme of the MCP resource URI. | `"file"`, `"http"`, `"https"` | #### [Example Resource Read Span:](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#example-resource-read-span) ```javascript // Example resource access const resourceUri = "file:///path/to/resource.txt"; await Sentry.startSpan( { op: "mcp.server", name: `resources/read ${resourceUri}`, }, async (span) => { // Set MCP-specific attributes span.setAttribute("mcp.resource.uri", resourceUri); span.setAttribute("mcp.method.name", "resources/read"); // Set request metadata span.setAttribute("mcp.request.id", "req_789ghi"); span.setAttribute("mcp.session.id", "session_xyz789"); span.setAttribute("mcp.transport", "http"); span.setAttribute("network.transport", "tcp"); // Access the resource const resourceData = readResource(resourceUri); }, ); ``` ## [Common Span Attributes](https://docs.sentry.io/platforms/javascript/guides/cloudflare/mcp-monitoring.md#common-span-attributes) The following attributes are common across all MCP span types and SHOULD be set when available: | Data Attribute | Type | Requirement Level | Description | Example | | ------------------- | ------ | ----------------- | ------------------------------------------------ | -------------------------- | | `mcp.transport` | string | recommended | The transport method used for MCP communication. | `"stdio"`, `"sse", "http"` | | `network.transport` | string | recommended | The network transport used. | `"pipe"`, `"tcp"` | | `mcp.session.id` | string | recommended | The session identifier for the MCP connection. | `"a1b2c3d4e5f6"` | | `mcp.request.id` | string | optional | The unique identifier for the MCP request. | `"req_123abc"` |