one check
Token counter
Paste a prompt, a document or the tool list of an MCP server and see how many tokens it is for GPT models, and for Claude where Anthropic's own counter is available. A tool list is split per tool, because an agent pays for it on every request.
How are the tokens counted?
GPT models use public encodings: o200k_base for GPT-4o, GPT-4.1, GPT-5 and the o-series, cl100k_base for GPT-4 and GPT-3.5. Both are counted exactly on our server. Claude uses its own tokenizer, which Anthropic does not publish, so Claude is counted only by Anthropic's counting endpoint and never estimated from a GPT count.
Why do Claude models count differently from each other?
Anthropic introduced a newer tokenizer with Claude Opus 4.7, and by its own account the same text comes out at about 30 percent more tokens than on earlier models. That is why the count runs against the model you pick rather than one number for all of Claude.
What does an MCP tool list cost?
A client sends the definition of every tool on every request, whether the agent uses a tool or not. Paste the answer of tools/list and the page counts the whole list and each tool on its own, so you can see which descriptions are worth shortening. In our own measurement Playwright MCP's 24 tools cost 3,162 tokens per request.
What does one step of a browser agent cost?
Usually far more than the tool list, because of what each answer carries. Before an agent could act on one Wikipedia page, Playwright MCP returned 604,785 tokens and Scalebrowser 2,771, counted with cl100k_base on 8 September 2026. The full measurement covers five browser tools and three sites.
Is my text stored?
No. It goes to our server, is counted and is gone. Do not paste secrets into any web form, this one included.