Hidden Cost Black Holes in MCP Tool Calls
C00LDude6ix9ine · reddit · 2026-07-15
While troubleshooting cost overruns across multiple agent systems, the author discovered that calculating costs per entire run reveals almost no waste; the real focus should be on the cost of individual MCP tool calls.
The post lists several common issues:
- The same tool being called repeatedly, often due to a lack of session-level caching
- Retrieval / memory looking like a "memory cost" when it actually includes massive embedding and retrieval overhead never used by the final answer
- Tool schemas and long descriptions being repeatedly counted as input tokens on every call
- Many observability dashboards only showing total agent costs, making it impossible to pinpoint "which tool is burning money"
The author offers a rough calculation: if a single tool call costs $0.003 and runs an extra 10,000 times daily, that one tool could add roughly $900 in monthly expenses.
More from coding & agent
- Alex Townsend posts 200 open problems in numerical linear algebra for humans and AI agents — IgorCarron · 2026-09-11
- Kimi K2.8 Preview rolls out: near-K3 coding performance, 1M context for all tiers — teortaxesTex · 2026-09-11
- Looking for a classifier of software engineering task shapes to pick models per task — StewartalsopIII · 2026-09-11
- Steal this idea: prompt-to-hardware where agents assemble custom devices — paraschopra · 2026-09-11
- Model Is the Least Interesting Part: A Guide to Six Core AI Architectures from RAG to Multi-Agent — goyalshaliniuk · 2026-09-11
- Non-coder builds layered memory architecture: 20k tokens tracks a year of agent conversations — matteoianni · 2026-09-11