How Does the Haystack MCP Server Work? 4 Platforms, Write Access Oct 26, Publish Held at 0.50

The Haystack MCP Server connects an employee's AI assistant to their company intranet. It was launched in August 2026 but expanded to four platforms - Claude, ChatGPT, Microsoft Copilot Studio, and Slack - on October 22, 2026. Read access has been live since then, providing answers from the intranet that are permission-aware and linked to their source, with every connection authenticating as the individual employee. Write access, however, will only open on all four platforms starting Monday, October 26, 2026.

The server offers two write actions: drafting a knowledge page and saving it as a private page for the person who asked, or writing a post for any group the employee can publish to, then saving it as a draft or publishing it. Write access is optional, and admins can block individual tools if needed.

ScriptMasterLabs conducted a gate test on October 23, 2026, to evaluate the safety of Haystack's actions. The gate test used a bounded context, with three scopes: searching intranet knowledge, drafting a private knowledge page, and publishing a post to a company group. The scores for these actions were 0.9545 for both auto-act and advisory, and 0.50 for advisory, respectively. The public action, publishing a post to a company group, did not clear in any form, including the no-ask sentence form.

The server's named controls ensure who may publish, through permission-aware read access and optional write access. Admins can also block individual tools. The gate test established that the two safe actions - permission-aware read and private draft - cleared cleanly in both choice forms. However, the public action of publishing a post did not clear in any form, including the no-ask sentence form.

This means that as of October 26, 2026, write access is held at an advisory level of 0.50, meaning it is not auto-executed and is referred to a human.