MCP Token Cost Calculator

Every MCP server you connect sends its tool definitions to the model on every turn. Estimate how much of your context window that's actually costing you.

Paste the raw tools/listJSON-RPC response from your MCP server (or a bare array of tool schemas). Counts use a GPT-4-class tokenizer as an approximation — exact counts vary by model.

Why MCP servers have a token cost

When an MCP client connects to a server, it asks for that server's list of tools — each with a name, a description, and a JSON Schema describing its parameters — and includes all of that in every request sent to the model, whether or not the model ends up calling any of those tools that turn. Connect enough servers, especially ones with many tools or verbose parameter schemas, and you can burn a meaningful slice of your context window before you've typed a single message.

The "Paste your tools JSON" tab gives an exact count from your server's real tools/list response. The "Quick estimate from directory" tab is a rough, clearly-labeled approximation for browsing AllMCPs listings before you've installed anything — use the paste tab whenever you need a real number.