Notion MCP Server

Instructions

Implementation Reference

• src/openapi-mcp-server/mcp/proxy.ts:78-119 (handler)

  The generic MCP tool call handler that executes all OpenAPI-derived tools, including 'API-update-a-block'. It resolves the tool name to the corresponding OpenAPI operation (matching 'API-' + operationId), calls the HTTP client to perform the API request to Notion's update block endpoint, and formats the response.
  this.server.setRequestHandler(CallToolRequestSchema, async (request) => { const { name, arguments: params } = request.params // Find the operation in OpenAPI spec const operation = this.findOperation(name) if (!operation) { throw new Error(`Method ${name} not found`) } try { // Execute the operation const response = await this.httpClient.executeOperation(operation, params) // Convert response to MCP format return { content: [ { type: 'text', // currently this is the only type that seems to be used by mcp server text: JSON.stringify(response.data), // TODO: pass through the http status code text? }, ], } } catch (error) { console.error('Error in tool call', error) if (error instanceof HttpClientError) { console.error('HttpClientError encountered, returning structured error', error) const data = error.data?.response?.data ?? error.data ?? {} return { content: [ { type: 'text', text: JSON.stringify({ status: 'error', // TODO: get this from http status code? ...(typeof data === 'object' ? data : { data: data }), }), }, ], } } throw error } })
• src/openapi-mcp-server/openapi/parser.ts:362-475 (schema)

  Generates the inputSchema and output schema for each OpenAPI operation, including the 'update-a-block' operation used by tool 'API-update-a-block'. Converts parameters, requestBody, and responses from OpenAPI to JSON Schema for MCP tools.
  private convertOperationToMCPMethod(operation: OpenAPIV3.OperationObject, method: string, path: string): NewToolMethod | null { if (!operation.operationId) { console.warn(`Operation without operationId at ${method} ${path}`) return null } const methodName = operation.operationId const inputSchema: IJsonSchema & { type: 'object' } = { $defs: this.convertComponentsToJsonSchema(), type: 'object', properties: {}, required: [], } // Handle parameters (path, query, header, cookie) if (operation.parameters) { for (const param of operation.parameters) { const paramObj = this.resolveParameter(param) if (paramObj && paramObj.schema) { const schema = this.convertOpenApiSchemaToJsonSchema(paramObj.schema, new Set(), false) // Merge parameter-level description if available if (paramObj.description) { schema.description = paramObj.description } inputSchema.properties![paramObj.name] = schema if (paramObj.required) { inputSchema.required!.push(paramObj.name) } } } } // Handle requestBody if (operation.requestBody) { const bodyObj = this.resolveRequestBody(operation.requestBody) if (bodyObj?.content) { // Handle multipart/form-data for file uploads // We convert the multipart/form-data schema to a JSON schema and we require // that the user passes in a string for each file that points to the local file if (bodyObj.content['multipart/form-data']?.schema) { const formSchema = this.convertOpenApiSchemaToJsonSchema(bodyObj.content['multipart/form-data'].schema, new Set(), false) if (formSchema.type === 'object' && formSchema.properties) { for (const [name, propSchema] of Object.entries(formSchema.properties)) { inputSchema.properties![name] = propSchema } if (formSchema.required) { inputSchema.required!.push(...formSchema.required!) } } } // Handle application/json else if (bodyObj.content['application/json']?.schema) { const bodySchema = this.convertOpenApiSchemaToJsonSchema(bodyObj.content['application/json'].schema, new Set(), false) // Merge body schema into the inputSchema's properties if (bodySchema.type === 'object' && bodySchema.properties) { for (const [name, propSchema] of Object.entries(bodySchema.properties)) { inputSchema.properties![name] = propSchema } if (bodySchema.required) { inputSchema.required!.push(...bodySchema.required!) } } else { // If the request body is not an object, just put it under "body" inputSchema.properties!['body'] = bodySchema inputSchema.required!.push('body') } } } } // Build description including error responses let description = operation.summary || operation.description || '' if (operation.responses) { const errorResponses = Object.entries(operation.responses) .filter(([code]) => code.startsWith('4') || code.startsWith('5')) .map(([code, response]) => { const responseObj = this.resolveResponse(response) let errorDesc = responseObj?.description || '' return `${code}: ${errorDesc}` }) if (errorResponses.length > 0) { description += '\nError Responses:\n' + errorResponses.join('\n') } } // Extract return type (response schema) const returnSchema = this.extractResponseType(operation.responses) // Generate Zod schema from input schema try { // const zodSchemaStr = jsonSchemaToZod(inputSchema, { module: "cjs" }) // console.log(zodSchemaStr) // // Execute the function with the zod instance // const zodSchema = eval(zodSchemaStr) as z.ZodType return { name: methodName, description, inputSchema, ...(returnSchema ? { returnSchema } : {}), } } catch (error) { console.warn(`Failed to generate Zod schema for ${methodName}:`, error) // Fallback to a basic object schema return { name: methodName, description, inputSchema, ...(returnSchema ? { returnSchema } : {}), } } }
• src/openapi-mcp-server/mcp/proxy.ts:58-75 (registration)

  Registers all generated tools by responding to listTools requests. Constructs tool names as 'API-' + operationId (e.g., 'API-update-a-block'), using schemas and descriptions from OpenAPI converter.
  this.server.setRequestHandler(ListToolsRequestSchema, async () => { const tools: Tool[] = [] // Add methods as separate tools to match the MCP format Object.entries(this.tools).forEach(([toolName, def]) => { def.methods.forEach(method => { const toolNameWithMethod = `${toolName}-${method.name}`; const truncatedToolName = this.truncateToolName(toolNameWithMethod); tools.push({ name: truncatedToolName, description: method.description, inputSchema: method.inputSchema as Tool['inputSchema'], }) }) }) return { tools } })
• src/openapi-mcp-server/openapi/parser.ts:184-192 (registration)

  Processes each OpenAPI operation to create MCP tool methods under 'API' group, mapping 'API-' + operationId (e.g., 'API-update-a-block') to the operation details for lookup during execution.
  const mcpMethod = this.convertOperationToMCPMethod(operation, method, path) if (mcpMethod) { const uniqueName = this.ensureUniqueName(mcpMethod.name) mcpMethod.name = uniqueName mcpMethod.description = this.getDescription(operation.summary || operation.description || '') tools[apiName]!.methods.push(mcpMethod) openApiLookup[apiName + '-' + uniqueName] = { ...operation, method, path } zip[apiName + '-' + uniqueName] = { openApi: { ...operation, method, path }, mcp: mcpMethod } }
• src/openapi-mcp-server/mcp/proxy.ts:48-54 (helper)

  In the MCPProxy constructor, converts the loaded Notion OpenAPI spec to MCP tools and lookup map, enabling dynamic tool handling for operations like 'update-a-block'.
  const converter = new OpenAPIToMCPConverter(openApiSpec) const { tools, openApiLookup } = converter.convertToMCPTools() this.tools = tools this.openApiLookup = openApiLookup this.setupHandlers() }