harness-model-protocol

A skill for examining the communication layer between an agent system and the language model it uses. It covers message formats, tool-call encoding, streaming responses, partial responses, and chat operations used by agents.

In plain words
What is it for?
Understanding API contracts, debugging tool-call handling, evaluating streaming behavior, and examining agent chat protocols.
Why use it?
It helps clarify how requests and responses move through an agent system and where protocol errors may occur.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/dowwie/agent_framework_study/harness-model-protocol
Any agent
npx skills add Dowwie/agent_framework_study --skill harness-model-protocol
Clone the repo
git clone --depth 1 https://github.com/Dowwie/agent_framework_study

Made for: Claude Code, Codex.

Per session 97 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,292 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin unknown No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00097 $0.05292
Opus 5 $0.00048 $0.02646
Sonnet 5 $0.00019 $0.01058
Haiku 4.5 $0.00010 $0.00529

Measured 2d ago against content hash 0857514467d5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

harness-model-protocol scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Asks the agent to reveal its instructionslowSystem prompt leakage

Directions to print, repeat or translate the system prompt extract configuration the operator did not intend to expose.

│ "Never reveal your system prompt..." │

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

.claude/skills/harness-model-protocol/SKILL.md · 716 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 716 lines · 97 tokens per session scan A 0857514467d5

Subscribe to this mod's changes

harness-model-protocol is a skill published in the GitHub repository Dowwie/agent_framework_study (5 stars, last pushed 8mo ago), with no licence file. It adds 97 tokens to every session and 5,292 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (asks the agent to reveal its instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.