Skill Retriever semantic skill discovery for AI agents via 10K-category taxonomy
Skill Retriever is an open-source semantic skill retrieval plugin for Hermes Agent. It pre-filters over 1,200 skills organized in a 10,000-category capability taxonomy to the top-5 most relevant per query, with zero additional API cost. It overcomes limitations of pure semantic retrieval by using LLM-navigated capability hierarchy to surface non-obvious but functionally relevant skills.
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ARCHITECTURE.md
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AgentSkillOS-powered semantic skill retrieval for Hermes Agent.
Pre-filters 1,200+ skills (998 community corpus + 211 Hermes skills) organized in a 10,000-category capability taxonomy to the top-5 most relevant per query. Runs as a Hermes pre_llm_call plugin — zero core modification, zero additional API cost (borrows your existing Hermes LLMs via borrow-mode).
Why a Skill Tree?
Pure semantic retrieval prioritizes textual similarity and misses skills that look unrelated in embedding space but are crucial for solving the task. Our LLM + Skill Tree navigates the capability hierarchy to surface non-obvious but functionally relevant skills.
Left: Pure semantic retrieval is narrow and myopic. Right: Skill Tree navigation surfaces functionally relevant skills the embedding space hides.
The Capability Tree
Skills are organized into a coarse-to-fine capability hierarchy. At scale, this is the difference between finding the right skill and drowning in an invisible pile.
The 10,000-category capability tree — the structure our 1,200 skills are mapped into.
How It Works
User Query │ ▼ ┌──────────────────────────────────────┐ │ pre_llm_call hook (plugin) │ │ Checks DISABLE flag, skips short Qs │ └──────────────┬───────────────────────┘ │ ▼ ┌──────────────────────────────────────┐ │ Searcher.search() │ │ 1. Load capability tree from YAML │ │ 2. LLM-navigate tree (select nodes) │ │ 3. Parallel child search (ThreadPool)│ │ 4. LLM prune (dedup + rank) │ └──────────────┬───────────────────────┘ │ ▼ ┌──────────────────────────────────────┐ │ Hint Injection │ │ Prepends top-5 skill hints as │ │ natural-language block. LLM may call │ │ skill_view(name) to load any. │ └──────────────────────────────────────┘
Why not just use Hermes OOTB?
Hermes already ships with skill discovery — every user-installed skill appears in the block of the system prompt. The LLM scans this flat list every turn and calls skill_view() when needed. For small sets it works fine.
skill-retriever adds a semantic retrieval layer that transforms skill discovery from "read the catalog" into "search for what you need":
Dimension Hermes OOTB skill-retriever
Skill source Your local ~/.hermes/skills/ only (~100-200) Community corpus (998) + Hermes skills (200) = 1,198 total
Discovery Flat name+desc list in system prompt every turn LLM-navigated taxonomy tree → top-5 relevant injected as hints
Token cost Every turn burns tokens for all skills, even irrelevant ones Zero system prompt overhead — hints only in user message, only when found
Categorization Filesystem directory names 10,000-category AgentSkillOS capability taxonomy
Scales to ~200 skills before prompt bloat 10K+ (tree handles it)
Latency per turn 0 (passive — always visible) +1-3 cheap LLM calls for tree traversal (when it has results)
Community corpus No Yes — 998 community skills alongside yours
The difference: OOTB gives you a flat skill catalog you read every turn. skill-retriever turns it into a search engine — describe what you need, the tree navigates to the right category, and only relevant suggestions appear. The tradeoff is a small latency cost per turn vs constant system prompt bloat.
Quick Start
git clone https://github.com/ChonSong/skill-retriever.git cd skill-retriever bash scripts/install.sh hermes gateway restart
Trust & Safety
Every skill carries a source tag and a safety scan result:
Badge Meaning
🔒hermes Installed via Hermes — trusted
🌐community From AgentSkillOS corpus — unreviewed
⚠️ (suffix) Flagged by safety scan — review before loading
All 1,200 skills were scanned for dangerous patterns (rm -rf /, curl | sh to raw IPs, base64 payloads, crypto miners). Zero flagged — every match was standard installer documentation inside code blocks.
CLI
python -m skill_retriever search "set up CI/CD pipeline" python -m skill_retriever build # rebuild capability tree python -m skill_retriever list # list all skills in corpus python -m skill_retriever info # system info + tree stats
Configuration
All settings via environment variables — no config files needed.
Env Variable Default Description
SKILL_RETRIEVER_DISABLE — Set 1 to disable entirely
SKILL_RETRIEVER_LLM_MODEL gpt-4o LLM model for skill gate
SKILL_RETRIEVER_LLM_API_KEY OPENAI_API_KEY API key
SKILL_RETRIEVER_LLM_BASE_URL OPENAI_BASE_URL Base URL
SKILL_RETRIEVER_BRANCHING_FACTOR 3 Tree branching (search)
SKILL_RETRIEVER_MAX_PARALLEL 5 Parallel search branches
SKILL_RETRIEVER_TEMPERATURE 0.3 LLM temperature
SKILL_RETRIEVER_PRUNE true Enable dedup/ranking step
SKILL_RETRIEVER_TREE_PATH bundled tree_10000.yaml Override capability tree
Architecture
See ARCHITECTURE.md for a technical deep-dive covering:
Capability tree structure and build process
LLM node selection algorithm
Searcher internals (parallel search, early stop, pruning)
Plugin hook integration
Directory layout
Requirements
Hermes Agent v0.18+
Python 3.10+
~500MB for capability tree index
~4GB for full skill corpus (optional, for rebuilding tree)
Project Structure
skill-retriever/ ├── plugin/ # Hermes plugin (pre_llm_call hook) ├── src/ │ ├── skill_retriever/ # Core engine │ │ ├── cli.py # CLI (search, build, list, info) │ │ ├── search/ # Searcher (multi-level LLM tree search) │ │ ├── tree/ # Tree builder, schema, prompts, scanner │ │ └── capability_tree/# Pre-built trees (YAML + HTML) │ └── scanner.py # Hermes skills scanner ├── data/ # Skill corpus (gitignored) ├── tests/ # 40 tests ├── scripts/install.sh # One-click Hermes plugin install └── ARCHITECTURE.md
License
MIT. Built on AgentSkillOS (MIT).
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AgentSkillOS-powered semantic skill retrieval for Hermes Agent.
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