This is interesting, because if I start a fresh session of Claude Code right now and run /context, I see the following:

   Opus 4.8 (1M context)
   claude-opus-4-8[1m]
   23k/1m tokens (2%) 

   Estimated usage by category
   System prompt: 3.9k tokens (0.4%)
   System tools: 13.9k tokens (1.4%)
   Custom agents: 235 tokens (0.0%)
   Memory files: 28 tokens (0.0%)
   Skills: 4.9k tokens (0.5%)
   Messages: 8 tokens (0.0%)
   Compact buffer: 3k tokens (0.3%)
   Free space: 974k (97.4%)

4k tokens is 15-20kB. I'd ask you to paste that into a gist, but it might have sensitive data in it, because I suspect what you're seeing is not just the system prompt.

Apologies, you're right - I used imprecise terminology. The entire initial JSON structure that was sent from Claude Claude to the LLM at the start of a session was 162k. This included the system prompt together with a list of tools (some with very extensive explanations), MCP server details, etc.

I was simply supporting the article's data - their reported 33k tokens is probably roughly 150-165k.

That’s entirely dependent on how many plugins, MCP tools, agents you have, and if you have pre-filling of all available tools enabled. Best way to avoid unnecessary expense is to avoid it all and use CLI tools instead.

Agree. It's a fairly minimal list with very few extras added.

Current /context on a fresh session (compare to that above) is:

  Opus 4.8
  15.8k/1m tokens (2%)
  System prompt: 4.5k tokens (0.4%)
  System tools: 7.9k tokens (0.8%)
  Memory files: 441 tokens (0.0%)
  Skills: 3.1k tokens (0.3%)
  Messages: 8 tokens (0.0%)
  Free space: 984.2k (98.4%)

A lot of people will just add as many tools as they can think of. I don’t think it’s obvious that this costs money.

A smarter approach (progressive disclosure) for tools has been implemented by (I presume all) the harnesses over recent months, but you're 100% right in any case.

I enable tools specific to each project only in that project, and have very very few in my global config. Like <5k tokens worth.

Ah that makes sense, wasn't trying to be pedantic. Thanks for clarifying.