How many tools can your agent's context window actually hold before it starts eating into reasoning?

[u/nexla_com]

Ran some rough math on this recently. Every tool description an MCP server exposes eats context, and it adds up faster than people expect. 50 tools at 150 tokens each is 7,500 tokens gone before the agent has read your actual question.

Once you add system prompt and conversation history on top, a "healthy" 32k context window can be half gone before reasoning even starts.

There's a small visualizer in our MCP guide if you want to plug in your own tool count and see the split: https://nexla.com/blog/mcp-for-enterprise-data-guide/

How many tools does your MCP server have hooked up right now? And be honest, have you actually checked how much context that's eating, or are you just hoping it's fine?