How Many Tokens MCP Tools Use in Cursor - The Hidden Cost

Fazm Team··2 min read

How Many Tokens MCP Tools Use in Cursor - The Hidden Cost

Every MCP tool you register has a schema definition. That schema gets sent with every request to the LLM so it knows what tools are available. 31 Atlassian tools burn 2-3k tokens before you even ask a question.

The Math Nobody Does

Each MCP tool definition includes a name, description, and JSON schema for parameters. A typical tool definition is 50-100 tokens. Connect a few MCP servers with 20-30 tools each, and you are spending 3-5k tokens per request just on tool definitions.

At scale, this adds up fast. If you make 100 requests per day and each one includes 4k tokens of tool definitions, that is 400k tokens per day spent on telling the LLM what it could do rather than what it should do.

Why This Gets Worse

MCP servers tend to expose every capability as a separate tool. An Atlassian integration does not give you one "manage Jira" tool - it gives you create_issue, update_issue, delete_issue, search_issues, get_issue, list_projects, and so on. Each one with a full parameter schema.

The more integrations you add, the worse the ratio gets. Your actual prompt might be 200 tokens. Your tool definitions might be 5k tokens.

How to Optimize

Prune unused tools. If you never use delete_issue from your AI editor, remove it. Most MCP servers let you configure which tools to expose.

Use CLI wrappers instead. A single "run shell command" tool with access to the Jira CLI costs far fewer tokens than 31 individual tool definitions. The tradeoff is less structured output, but the token savings are significant.

Lazy-load tool schemas. Some frameworks support loading tool definitions only when relevant to the current task. This keeps the baseline token cost low.

The Real Question

Before adding an MCP server, ask whether you will use more than 3-4 of its tools regularly. If not, a CLI wrapper or a focused custom tool will serve you better at a fraction of the token cost.

Fazm is an open source macOS AI agent. Open source on GitHub.

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