MCP Agents Cost Up to 18x More Tokens Than CLI Tools, Benchmarks Show

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New benchmarks comparing CLI and MCP-based AI agents on identical GitHub tasks found CLI to be 10 to 32 times cheaper and fully reliable, while MCP succeeded only 72% of the time. A key driver of MCP's higher cost is schema overhead: every connected MCP server injects tool definitions into the model's context on every request, regardless of whether those tools are used. A study of 3,875 MCP servers found a median of 2,064 tokens per server in definition overhead, with a GitHub MCP server alone consuming over 14,000 tokens. Perplexity's CTO noted that MCP tool descriptions occupied 72% of the available context window before any real work began. Across 100 operations, a tool-call-oriented agent costs roughly $0.17 compared to $3.11 for an unfiltered raw-command approach, but running five MCP servers simultaneously can add over 10,000 tokens of idle schema overhead per request.

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