What MCP servers cost in context
Claude Code puts every MCP tool's definition, and one line per skill, command and plugin agent, into every request, before your conversation starts. We counted those tokens exactly (Anthropic's free token counter, no model calls) for 9 open-source MCP servers and the 29 plugins of the official marketplace.
The short answer
- MCP servers cost far more than skills. The 9 servers add 68,819 tokens; all 29 plugins together add 10,874.
- One large server can outweigh everything else: Notion's 24 tools take 33,442 tokens.
- On Opus 5.5, carrying 1,000 always-loaded tokens through a 100-turn session costs $0.0248.
- When the client loads tool definitions only on demand and lists names, the same 9 servers take 2,282 tokens: 3% of the full load.
Per server (full definitions)
| Server | Tools | Tokens |
|---|---|---|
| notion | 24 | 33,442 |
| chrome-devtools | 32 | 11,177 |
| playwright | 25 | 6,710 |
| github | 26 | 6,532 |
| filesystem | 14 | 2,983 |
| everything | 16 | 2,962 |
| memory | 9 | 1,756 |
| context7 | 2 | 1,725 |
| sequential-thinking | 1 | 1,532 |
Per setup, 100-turn Opus 5.5 session
| Setup | Tokens loaded | Cost per session | Per turn | Names only |
|---|---|---|---|---|
| Light: 2 plugins, 1 MCP | 1,817 | $0.045 | $0.00045 | 119 tokens |
| Typical: 8 plugins, 3 MCPs | 19,033 | $0.47 | $0.0047 | 4,809 tokens, $0.12 |
| Heavy: 29 plugins, 9 MCPs | 79,693 | $1.98 | $0.020 | 13,156 tokens, $0.33 |
Opus 5.5 list prices: $4 per million input tokens, $0.20 per million cache reads. The context is written to the 5-minute cache once and read on the other 99 turns. With a 1-hour cache write: light $0.051, typical $0.53, heavy $2.22.
What this does not say
- It is a floor: cache expiry, rebuilds and compaction make the real cost higher.
- It measures cost, not benefit. A server you use can save far more than it costs; remove only what you don't use.
- Hosted servers (Slack, Linear, Gmail and others) were not measured, and token counts change with each server version.
- On a subscription plan this is plan usage, not cash.