Here is the query client asked me:

We have a question regarding the accessibility of charts on our platform. We are unsure if charts can be viewed as ‘complex images’ and therefore only require descriptive measures, or of charts have to comply to other WCAG criteria as well. We are particularly looking into: 
•	1.4.1 Use of color
•	1.4.11 Non-text contrast 
 
If these criteria need to be met for charts, we have explored some possible solutions like adding space between the elements and a darker border, and the use of a tooltip to not rely on color alone. We are curious to learn if these criteria need to be met for charts, and if so, if these solutions would be sufficient or not and if there are any other criteria that need attention as well. 

Here is the answer I prepared:

Charts are indeed considered under WCAG guidelines, and they require attention to various criteria to ensure accessibility, including but not limited to “Use of Color” (1.4.1) and “Non-text Contrast” (1.4.11). Here are the descriptions for WCAG 1.4.1 and WCAG 1.4.11:

1.4.1 Use of Color: This guideline states that color should not be the only means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.

For charts, relying solely on color differences to differentiate elements does not comply with this criterion. It’s imperative to use patterns or shapes to differentiate elements, ensuring accessibility for users with color vision deficiencies. Patterns or shapes provide a fundamental solution for conveying information that is not dependent on color perception. Additionally, while tooltips can offer valuable textual information when elements are hovered over or selected, it’s important to note their limitations on mobile platforms, where hover interactions are not available. This limitation makes tooltips a less reliable sole strategy for conveying essential information on these devices. Therefore, incorporating patterns or shapes is strongly recommended to ensure broad accessibility, with tooltips serving as a complementary, but not primary, method for providing information.

1.4.11 Non-text Contrast: This criterion refers to the visual presentation of UI components and graphical objects having a contrast ratio of at least 3:1 against adjacent colors for their states and boundaries.

For charts, ensuring that graphical elements like axes, lines, and data points stand out sufficiently against the background or other elements is crucial. The current idea of adding dark borders and increasing the spacing between elements can enhance the visibility and legibility of charts. However, it’s essential to manually check the contrast ratios to ensure they meet the minimum requirements. Tools like Color Contrast Analyzer (CCA) can be helpful.

To summarize, charts on your platform need to comply with WCAG guidelines, particularly those concerning the use of color and non-text contrast. Adopting patterns or shapes to distinguish elements is essential for meeting accessibility standards, especially for users with color vision deficiencies. While employing tooltips, increasing spacing, and enhancing borders contribute positively, it’s crucial to recognize tooltips’ limitations on mobile platforms. Therefore, a comprehensive approach to accessibility that combines visual differentiation with alternative ways to access information is key.

Your task is to add below points:
1. "We are assuming that the charts mentioned below are the static charts.": You need to add this before my statement. Correct the verbiage accordingly.
2. Provide alternative textual descriptions for charts. This ensures that screen reader users are able to comprehend the charts properly.: This needs to be included somewhere in the response. Use your judgement to add the response in the appropriate location.