sentry.engineering
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ksl
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Sentry’s engineering team ran a controlled comparison of three approaches to AI-assisted iOS builds: raw shell, a primed shell with an AGENTS.md config file, and XcodeBuildMCP. All three hit 99%+ success rates – the differences showed up in cost and speed. A plain markdown file with build parameters finished 34% faster and used 15% fewer tokens than the MCP route. The reason is straightforward: MCP tools inject schemas upfront that eat into context budgets before the agent does anything useful. XcodeBuildMCP v2 narrowed the gap with stateful sessions and trimmed schemas, and its real advantage kicks in for closed-loop workflows requiring screenshot capture, view hierarchy inspection, and runtime debugging. The broader pattern across teams adopting MCP servers tracks with this finding – most reach for them too early when a config file would do.
