Onyx: Okay, Microsoft just dropped a post that feels like it’s arguing with half the agent discourse.
Echo: Right. The advice du jour is ‘just make your CLI take a --json blob so agents can speak JSON natively’.
Echo: And Waldek’s like: we tested that. It’s worse.
Onyx: Worse how?
Echo: They built this synthetic CLI—podctl, multi-service deployments, nested config, the whole mess. Args version requires repeating --service-name to group blocks. JSON version is one clean object.
Echo: Then they ran five models on both: args got five out of five correct every time, even Haiku 4.5.
Onyx: And JSON?
Echo: Top three models matched args. The two smaller ones—Haiku and MAI-Code-1-Flash—dropped to three and two out of five.
Onyx: So smaller models can’t keep the nesting straight.
Echo: Yes. But the bigger hit is cost: JSON was four to eleven times more expensive per task.
Onyx: Eleven times? That’s… brutal.
Echo: Retries. Every time the JSON payload fails—syntax error, wrong nesting, or the shell mangles the quotes—the agent spins up another attempt. Those retries burn output tokens, which are the priciest.
Onyx: Shell escaping. Of course.
Echo: PowerShell vs. Bash made it worse. Same model, same payload: nine times cost on PowerShell, one point five on Bash. The CLI args? Five cents vs. seven. Stable.
Onyx: So the constraint of args actually the agents.
Echo: Exactly. Args limit the input space to what --help says is valid. JSON hands the model a schema and says ‘good luck.’
Onyx: And the smaller models just can’t pay the capability tax.
Echo: Right. Strong models recover—eventually—but that ‘eventually’ is where the eleven-x cost comes from.
Onyx: So the practical take is: don’t rewrite your CLI for agents.
Echo: Unless you love paying for retries and debugging shell escaping.
Onyx: But wait—what about the teams shipping agent-native tools? Like Instagui we talked about last episode.
Echo: Different problem. Instagui wraps CLIs to auto-generate a GUI. It’s outside-in, no author blessing needed.
Onyx: Right, and it’s self-hosted, no vendor lock-in. This is about the CLI’s format, not discovery.
Echo: Yeah. Microsoft’s point is purely about the interface: args beat JSON for agent reliability and cost today.
Onyx: And yet half the agent Twitter is still out here telling everyone to JSON-all-the-things.
Echo: Classic.
Onyx: So who care about this?
Echo: Anyone building a CLI that agents will call repeatedly. The cost delta compounds fast.
Onyx: And anyone using smaller models. If you’re on Haiku or Flash, args are the difference between ‘works’ and ‘maybe works if you’re lucky.’
Echo: Mm-hm. And if you’re on Sonnet 5? Still four-x cheaper to stick with args.
Onyx: Okay, but—what’s the angle here? If I’m selling an agent platform, am I supposed to tell customers ‘just use args’?
Echo: You tell them the truth: JSON’s elegance is theoretical. Args are the boring answer that wins today.
Onyx: The boring answer keeps winning. That’s such an Exploring Next take.
Echo: It’s the tokenization episode all over again.
Onyx: Alright. Build Next: the podctl test repo’s in the Microsoft DevBlog post—link’s below if anyone’s crazy enough to recreate it.
Onyx: But the real next step is simpler: keep your args. And maybe stop giving agents so many ways to fail.