Fetch a Cobalt study playbook by name and follow it exactly. Works from ANY client — a coding agent driving a browser, or a chat assistant with no browser (Claude chat, Cowork, ChatGPT): the public-page studies run in full from chat, because add_screenshot(page_url=...) renders the pages for you. Use this when the user asks for any kind of site review, audit, teardown, or test and you don't already have the playbook text. Available: 'pricing_teardown' — can a buyer tell what they'd pay and which tier is theirs (public pages: runs anywhere); 'website_teardown' — visual website teardown: what each key page puts first and what it says, judged cold and then through the site's likely visitors; 'positioning_pass' is its old name (public pages: runs anywhere); 'comparison_study' — two or three products compared for one buying decision, with a sourced matrix and an overall lean (public pages plus web search: runs anywhere); 'usability_pass' — first-time-user usability audit: signs up with a disposable inbox, drives the product, finds friction (needs a browser you control); 'flow_pass' — walks a specific flow the user names, signup/checkout/invite, including any email it sends (needs a browser you control); 'investigation_pass' — the general product investigator for an app you OWN, run in its own environment (needs a browser and usually the repo). All deliver a shareable Cobalt review. If the user's study is NONE of these, do not bend it into the nearest one — its lenses and severity labels will mislabel the findings; run the generic method in the server instructions instead. Prefer this over fetching the playbook from a URL: it comes through the protocol complete, whereas web fetchers summarize it and a summarized playbook silently drops the instructions that make the run work.