Asim Aslam
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The Agent Harness
The first wave of agent frameworks solved one problem: put a model in a loop with some tools. The harder problem is operating that loop — and that's what a harness is.
A harness is the runtime around an agent:
- the tools it can call,
- the memory it keeps,
- the guardrails that bound it,
- the workflows that trigger and structure it,
- the state that survives a restart,
- the observability to see what it did,
- the services it depends on,
- and the protocols other agents use to reach it.
Go Micro's bet is that this runtime is the one you already deploy. An agent is a service with a model inside; the harness is the distributed-systems machinery services already have. So you don't bolt a separate orchestration product onto your stack — the harness is the stack.
The pieces, and what they map to
| Harness concern | In Go Micro | Status |
|---|---|---|
| Tools | Every service endpoint is an MCP-callable tool from registry metadata — no extra code | Shipped |
| Memory | Store-backed agent memory (AgentMemory), durable across restarts |
Shipped |
| Guardrails | MaxSteps, LoopLimit, ApproveTool, tool wrappers — enforced at the call site |
Shipped |
| Workflows | Durable flows; flow.Loop for run-until-done |
Shipped |
| Planning / delegation | Built-in plan and delegate tools on every agent |
Shipped |
| Discovery & RPC | Registry + client; agents and services find and call each other | Shipped |
| Interop | MCP (tools), A2A (agents), x402 (paid tools) | Shipped |
| Resilience | Per-call timeout with context propagation; opt-in retry/backoff (ModelRetry) across the loop |
Shipped |
| Durable runs | Checkpoint and resume an agent run (flows already do) | In progress |
| Observability | RunInfo → OpenTelemetry spans; run history on the CLI |
In progress |
| Streaming | ai.Stream through chat, agent, and A2A |
In progress |
The "in progress" rows are exactly the roadmap's Now and Next, and the work is happening in the open.
Why services are the right substrate
An agent that does real work needs typed, discoverable, callable capabilities — which is what a service is. The harness is credible because of the service layer, not in spite of it:
- Tools are services — endpoint metadata becomes the tool schema; an RPC executes the call.
- Agents are services — they register, load-balance, expose
Agent.Chat, and are reachable by other agents. - Workflows are code paths — use a flow when the path is known; hand off to an agent when it isn't.
- Safety lives at execution — guardrails run on the one path every tool call takes.
When to reach for it
Use Go Micro when the agent has to operate a system, not just answer a prompt — when it needs real tools, state that survives, limits you can enforce, and a way to be seen and called. If you only need a model in a loop, you don't need a harness. When that loop has to touch production, you do.
See also
- Agents and Workflows — flows vs. agents
- Agent Loops — run-until-done, with a ceiling
- Plan & Delegate
- Agent Guardrails
- Provider Conformance — verified provider behavior
- Roadmap