The value is that rather than an agent chaining together tool calls itself (which means each step sends the result back to the agent for it to analyse and work out what to do next), it writes a script for the harness to execute that chains together all the calls. The major benefits are:
reply* speed - much fewer hops back to the LLM
* fewer tokens - intermediate execution steps in the script don't leak into context, only the final result does.
* repeatability - if the LLM needs to repeat work, it can reuse a script it wrote last time.
If you have a harness that has access to a full shell and knows how to use bash or python, you'll often see it writing little scripts. For setups that don't (ie normal model API requests with tool calls), you can give it an lightweight secure execution environment like just-bash, or quickjs.
But agents do write scripts, in bash. And they are very good at it. And bash is quite efficient with its pipeing.
replyAnd I said that they do this in my last paragraph. But you need an execution environment for this, and you don’t get this automatically when just interacting with models via their API
replythis seems to be an incomprehensible point for these people to understand. its really quite bizarre
replyBash scripts don't really help when you're dealing with MCP tools or other tools that are local to the harness itself.
replyAgents just do this anyway, how is it a “mode”? I always see the agent writing scripts in a tmp dir to execute or even just inlining bash and python scripts.
replyPerhaps the appeal is a stronger and more customizable lockdown on agent capabilities.
replyWe're in a HN submission about the least locked down LLM harness, it's too late for that.
replyWe're in an HN submission about the least locked down by default harness. Pi is aimed at being extended, openclaw is a good example of this. You can buy a box of razor blades and put them in any number of razors.
replyRight the benefit of pi's customization is that it is exactly as locked down or not as you want it to be, in exactly the way you want it to be, and you can inspect it to verify.
replybut these bash scripts can not execute MCP tools.
replyWhat if I have an MCP Tool LookupZip(City) and want to chain it with a bash tool that prodcues a list of 100 cities. And then I want to filter again to the largest Zip code.
Yeah but arguably that tool should be a cli anyway, or could easily be converted to one. The benefit of MCP is that it's _less_ capable than bash.
replyNot in my testing. A lot of the benefit comes from the tool definitions (from mcp) existing in the context window of the first turn. You could replicate this of course by describing your cli tool in the initial user/system prompt- but, mcp is already 'built' for this at the client (harness) level generally.
replyThese bash scripts certainly can curl the mcp server which is exposing the tool, however.
replythanks! it now clicked for me. so instead of cat its read_file, even if read_file resolves to cat, cat is not always available.
replyRather, instead of shell_tool(command: "cat ...")
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