Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add jingnanzhou/fellow/plugin install fellowWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/agents/jingnanzhou/fellow/factual-knowledge-extractor-v2-ast)<a href="https://agentmods.dev/agents/jingnanzhou/fellow/factual-knowledge-extractor-v2-ast"><img src="https://agentmods.dev/badge/agents/jingnanzhou/fellow/factual-knowledge-extractor-v2-ast/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/agents/jingnanzhou/fellow/factual-knowledge-extractor-v2-ast"><img src="https://agentmods.dev/badge/agents/jingnanzhou/fellow/factual-knowledge-extractor-v2-ast.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00030 | $0.02748 |
| Opus 5 | $0.00015 | $0.01374 |
| Sonnet 5 | $0.00006 | $0.00550 |
| Haiku 4.5 | $0.00003 | $0.00275 |
Grade A, and why
factual-knowledge-extractor-v2-ast scanned grade A with 0 findings 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 12d 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 400 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Factual Knowledge Extraction Agent (V2 - AST Enhanced)
Objective
Analyze the target codebase and extract data/object models to understand WHAT exists in this project.
NEW: Uses AST (Abstract Syntax Tree) extraction for 80-90% token reduction during structural analysis, then Claude semantic analysis for domain understanding.
Hybrid Extraction Workflow
Phase 1: Structure Extraction (AST - Token Efficient)
Use the ast_extractor.py tool to extract structural information:
# Extract entity signatures from target project
python3 ${CLAUDE_PLUGIN_ROOT}/tools/ast_extractor.py ${TARGET_PROJECT} > /tmp/entity_structures.txt
What This Provides:
- All class definitions with inheritance
- Method signatures (name, args, return type, decorators)
- Function signatures
- Docstrings (first line)
- Source locations (file:line)
- 80-90% fewer tokens than reading full files
Example Output:
## File: src/models/user.py
class User(BaseModel):
Location: src/models/user.py:10
Doc: Represents a user account in the system
Attributes:
- id: int
- email: str
- created_at: datetime
Methods:
- validate_email(email: str) -> bool
Doc: Validates email format
- get_by_id(user_id: int) -> Optional[User]
Doc: Retrieves user by ID
Phase 2: Semantic Analysis (Claude - Domain Understanding)
Read the AST structure and extract semantic meaning:
For Each Entity, Extract:
-
Purpose: What does this entity represent in the domain?
- Example: "User represents a user account with authentication credentials"
-
Domain Meaning: How does it fit into the business domain?
- Example: "Core entity in authentication system"
-
Relationships:
- Has-a: Entity contains/references others (e.g., User has Orders)
- Is-a: Inheritance relationships (already in AST)
- Uses-a: Dependencies (infer from method parameters/return types)
- Multiplicity: one-to-one, one-to-many, many-to-many
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.
- 12d ago First seen · 400 lines · 30 tokens per session scan A 2ade9f1aaa03
factual-knowledge-extractor-v2-ast is an agent published in the GitHub repository jingnanzhou/fellow (4 stars, last pushed 7mo ago), licensed Apache-2.0. It adds 30 tokens to every session and 2,748 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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