Tool
How much context do your MCP tools cost?
Every MCP server you connect loads its tool definitions into the model’s context window and re-sends them on every turn. Drag the slider to see what that costs as you scale up — and what an aggregating gateway does to the same surface. Built on 34 real connectors: ~21× smaller on the curated tool set, plus ~17,058 further actions only the gateway can reach.
Default 34 = our connected stack on 11 July 2026 (external tools only; internal tools excluded). Drag higher to model growth.
Direct MCP — curated tools resident
–
tokens, re-sent every turn
Via the gateway — resident
–
tokens — flat per service
How these numbers are derived
- Direct MCP here is the curated tool set a normal MCP server exposes — not the entire API (nobody loads 12,000 tools). For REST connectors it is estimated from each connector’s curated action specs; for MCP-proxy servers (Amplitude, Figma, Windmill) it is measured live from their
tools/listresponse. - Via the gateway is the measured resident cost of the read/write wrapper tools — a flat 550 tokens per service (460–640 measured), which does not grow with a service’s action count.
- The long tail is the gateway’s bonus, not the baseline: across these connectors ~17,058 further actions exist beyond the curated set (Microsoft 365 alone: 14 curated tools but 12,082 long-tail actions). Loaded as raw tools they are unusable; the gateway keeps them reachable via on-demand search at roughly zero resident cost.
- The slider models the average curated set across the 34 connectors (~11k tokens/service). Per service the gap ranges widely — lean connectors are modest, verbose ones (Amplitude) hit the 300×+ the article measured. Figures are estimates (character-based where not directly tokenized); measured 2026-07-11.
The full write-up, with charts and sources: The token cost of MCP tool definitions — measured.