Every Claude Code request carries a payload you never typed: MCP tool schemas, a skills catalogue, instructions for features you may never touch. The advice going around is to cut it, and the tool people reach for is Matt Pocock's logging proxy, which records every request between the CLI and the API.
I ran it. Its first log said:
**93,780 input tokens** billed for this request (from the response usage).The raw usage in the same file said:
{"input_tokens": 2, "cache_creation_input_tokens": 340,
"cache_read_input_tokens": 93438,
"cache_creation": {"ephemeral_5m_input_tokens": 0,
"ephemeral_1h_input_tokens": 340},
"output_tokens": 178}Two tokens at the base rate.
Why is the headline number wrong?
The sum is legitimate. Anthropic's prompt caching docs define total_input_tokens as exactly that addition. The prices are not equal: a 5-minute cache write costs 1.25x base, a 1-hour write 2x, a cache read 0.1x. Mine was a 1-hour write.
| field | tokens | rate | equivalent |
|---|---|---|---|
input_tokens | 2 | 1x | 2 |
cache_creation_input_tokens (1 hour) | 340 | 2x | 680 |
cache_read_input_tokens | 93,438 | 0.1x | 9,344 |
| proxy headline | 93,780 | 10,026 |
Nine point four times, from summing three prices as one.
Why did everything land in cache_read? The docs define input_tokens as the tokens after the last cache breakpoint, and mine was 2. The schemas and system prompt sat ahead of it and don't change between turns: a large stable prefix, a small variable suffix, the ideal shape for caching. The payload everyone panics about is the part that caches best.
Cache reads are 10% of base, not 0%, and every fresh session pays a 1-hour write at 2x to lay the prefix down again. A ninth as expensive is not the same as cheap.
The scarce thing is your context window
Tool definitions consume space and attention. The model reads past all of them before reaching your question, and picks from a longer list. /context shows where they go. Mine, copied as printed:
99.1k/1m tokens (10%)
System prompt: 3.1k
System tools: 6.1k
MCP tools: 43k ← 127 tools
Custom agents: 1.1k
Memory files: 8.6k
Skills: 9.8k ← 494 skills
Messages: 28.5k43k of MCP. Not the system prompt at 3.1k, which no setting of mine can shrink. Not the skills catalogue, which sounds enormous at 494 entries and costs 9.8k.
A spreadsheet server was my largest line item. 26 tools, 33 KB, on every request I had ever sent. I have never once asked Claude to open a spreadsheet.
Check what your projects import
The obvious move is to delete anything you don't recognise. I nearly did, and would have broken two of my own apps. So I grepped every package.json on the machine for the packages behind each server instead.
Ten repositories, and the answer contradicted my instinct. expo was in two, including my training app. @supabase/supabase-js in two more. prisma and stripe live in a third. All four were on my cut list only because the project I happened to be sitting in didn't use them, which is the wrong question when the setting is global. mongodb, playwright, and @auth0/* came back empty across all ten.
That test only works for servers backed by an npm dependency. My 33 KB spreadsheet server has no package to grep for, so nothing in that output justified cutting it. I cut it on the sentence above, which is a judgement, and I'd rather label it as one than dress it up as a measurement.
The result: 43k of MCP down to zero
19 plugins removed, 16 kept. Then /context again:
25.9k/1m tokens (3%)
System prompt: 3.2k
Custom agents: 1k
Memory files: 8.6k
Skills: 9.9k ← 254 skills
Messages: 3.1k
MCP tools · /mcp (loaded on-demand)
16 tools · 0 tokens111 of 127 tool schemas gone. Three things I won't claim from that.
I can't tell you why the line reads 0. The second reading carries a label the first didn't: loaded on-demand. Whether my cut triggered that mode, or whether it would have fired anyway with all 35 plugins installed, I couldn't determine. I went looking in the binary, found the deferral machinery, and couldn't isolate the condition. An earlier session had tools deferred with every plugin still enabled, which points against my instinct.
99.1k to 25.9k isn't mine either. Messages fell 28.5k to 3.1k because the second reading was a fresh session.
I'm not counting the 6.1k of system tools that vanished between readings. Removing MCP plugins shouldn't remove Claude Code's built-ins, and a number without a mechanism is what this post is complaining about. Attributable: 43k.
The half that did nothing: 240 skills, no change
Those 19 plugins took their skills with them, 494 entries down to 254. The skills line went from 9.8k to 9.9k.
It went up. Make that a fourth thing I can't explain: at roughly 16 bytes per bare entry, losing 240 of them should have taken about 1k off, and instead the line gained 0.1k. Rounding moves 0.1k, not 1k, and it doesn't move a number the wrong way.
What I can measure is the shape. The catalogue is one line per skill, and most lines are a bare name worth about 16 bytes. Of the 173 skills in my home directory, the set I can open and count, 147 were bare and cost 2.3 KB between them, while 26 carried 12 KB. I'm assuming the 240 plugin entries that vanished skewed the same way, which I can't verify now that they're gone.
Either way the count was never the cost, so cutting the long tail is theatre. Whether the expensive minority can be trimmed is a question I haven't answered, and after watching this line move the wrong way I'd want to measure it before believing anyone who says it can. Including me. That instinct is the whole of why AI builds the plausible feature, not yours: the confident answer and the correct one are different things.
What to do
Run /context before touching a setting. If it's the system prompt at 3.1k, there's nothing to win. If it's MCP, list what your projects import rather than what you remember installing.
And read the proxy's request body, which is what it's genuinely good at. Its per-tool ranking found the 33 KB server I'd been shipping for months. Just don't let the headline send you looking for a bill that was never there.
For the version of this argument where the numbers do carry a dollar sign, see what an eval harness caught that a bigger model couldn't, or the rest of the levers in production LLM cost optimization.