SkillMarker: A KGW-Based Watermarking Method for Agent Skill Ownership Verification

SkillMarker. A KGW-Based Watermarking Method for Agent Skill Ownership Verification. By Alan Tang and five others, from Huawei and the Harbin Institute of Technology, Shenzhen. Published on the eleventh of October. Its code repository is public but slight: one source file.

Agent skills encode operational procedures and domain expertise as reusable knowledge assets. They are distributed in plaintext, which exposes them to unauthorized copying and leakage, and practical ways to verify who owns a skill, or to trace where one leaked, remain underdeveloped. Embedding a watermark before distribution is a potential answer. The difficulty is the material itself. Skill instructions are structured and compact, and they must stay factually and procedurally accurate, so there is very little slack in the text to carry a mark without damaging what it tells an agent to do.

SkillMarker is a watermarking method based on KGW that aims at two targets together: preserving functionality, and embedding a strong watermark. It unifies two components. One is quality-constrained rewriting. The other is signal-oriented candidate search.

The rewriting separates essential knowledge from flexible expression, so the parts that carry instruction fidelity are preserved while the wording around them is free to change. The search then explores alternative expressions within those preservation constraints, looking for the ones that give a stronger watermark signal. One component guards what the skill says, and the other makes the most of how it can be said.

The work comes with an open-source toolkit that integrates watermark embedding, quality auditing, and detection, built to support the protection of agent skills.

The intended setting is a distributed skill ecosystem, where content may be copied in whole, copied in part, or incorporated into other skills. Ownership verification and leakage tracing are the two jobs the watermark is meant to do there. The tension SkillMarker is built around is that the mark has to live inside text whose every step must still work.