mcp-cli

That's a harness concern, not a protocol concern. For example, maki [0] allows that automatically for all tools > code_execution tool - uses monty to run an interpreter that has all other tools available as async functions. Maki uses it to filter / summarize / transform / pipe data to other tools as input, without it ever reaching and polluting the context window. Sandbox limited by time & memory. Failing that, you can just disable native MCP in your harness and have your agent use a CLI tool that calls MCP, like mcp-cli [1], and then the agent can use regular unix pipes to filter or transform the output. Here, rather than raw grep or sed (which are line oriented), the agent would probably use things like jq. [0] https://github.com/tontinton/maki#context-efficiency [1] https://github.com/philschmid/mcp-cli