Cursor loads MCP tools on demand: what it means for Sume
Cursor says dynamic MCP context cut total tokens 46.9% in sessions that call an MCP tool. For Sume, keep the tool list short and use tools_list.
Cursor's September 23, 2026 post says it moved MCP tool descriptions into dynamic context, loaded only when needed, and that this cut total tokens by 46.9% across sessions that called an MCP tool. If you connect Cursor to Sume's hosted MCP, the server's own two-step discovery works with that design: names first, one schema on demand.
The numbers are Cursor's, from its token efficiency post, and they describe Cursor's sessions. This post does not claim a figure for Sume.
What Cursor changed
| Item | What the post says |
|---|---|
| MCP tools | Moved into dynamic context, loaded only when needed |
| Reduction | 46.9% fewer total tokens in sessions that called an MCP tool |
| High-frequency tools | Stay in static context |
| Overall | 7% cost reduction; system prompt trimmed about 66% |
How does this help with a big tool list?
Sume exposes assets, generation, crawl, avatar and timeline tools. The hosted MCP docs list discovery tools (mcp_health, tools_list, tools_schema, account_me, catalog_list), and a client can ask tools_list for names and tools_schema for one tool at a time.
With on-demand loading in the client, a session that only needs a crawl read never pays to describe video generation. If your session needs a single tool every turn, that is the case Cursor keeps static, so use the editor's own settings to see how it classifies it.
Tips for a Cursor setup
- Connect with OAuth and accept
mcp:readfirst; addmcp:writeonly for paid work. - Ask the agent to call
tools_listand report the names before it picks one. - Do not copy Cursor's percentage into your own reports.
- Re-read the Cursor post; its defaults may change.
Sources
Related posts
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Written by Sume