Specification Subgraph Extractor

What it does

When your agent uses it

• Converting a protocol or specification document into formal program graphs
• Producing Mermaid diagrams of function and state-transition logic from a spec
• Feeding graph inputs to a specification-based audit pipeline

Example prompts

• “Extract program graphs from the beacon chain specification at this URL and write the .mmd files to ./graphs.”
• “Break the EIP-7594 specification into functional units and draw one program graph for each.”
• “Which validation flows in this spec can be drawn as program graphs? Extract them into Mermaid files.”

Requirements

• Fetch access to the specification URL, or a local copy of it
• A writable output directory
• Pre-approved tools (allowed-tools): read, write, mcp__fetch__fetch, mcp__filesystem__write_text_file, mcp__tree_sitter__get_symbols, mcp__tree_sitter__run_query

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

1. 1Read Specification: If local_path is provided and the file exists, read from it. Otherwise, fetch the content from url using mcpfetchfetch.
2. 2Identify Functional Units: Break down the document into logical units
3. 3Extract Program Graph Components
4. 4Generate Mermaid Diagrams: For each program graph, write a .mmd file to
5. 5Return Result: Return the JSON structure described in Output Format below. Do not write index.json — the calling worker handles aggregation.

What it can do on your machine

Read from SKILL.md and the folder at commit d173893. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • read
  • write
  • mcp__fetch__fetch
  • mcp__filesystem__write_text_file
  • mcp__tree_sitter__get_symbols
  • mcp__tree_sitter__run_query

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are mermaid and json).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Specification Subgraph Extractor loads about 1.6k tokens when it runs. Until then it costs about 32 tokens; SKILL.md has 560 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~32

When it runs · the whole SKILL.md, loaded when a task matches

~1.6k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from NyxFoundation/speca at commit d173893, republished under its MIT licence (© NyxFoundation). 560 words, ~1,629 tokens.

name

subgraph-extractor

description

Extract program graphs from a single specification document following Nielson & Nielson's formal definition.

allowed-tools

read, write, mcp__fetch__fetch, mcp__filesystem__write_text_file, mcp__tree_sitter__get_symbols, mcp__tree_sitter__run_query

context

fork

---
title: "factorial (Example Spec)"
---
stateDiagram-v2
    direction TB
    [*] --> q1: y = 1
    q1 --> q2: x > 0
    q1 --> [*]: x <= 0
    q2 --> q3: y = x * y
    q3 --> q1: x = x - 1

    note right of q3
        INV-001: y equals x! at loop termination
    end note

[*] --> q1 : y := 1     # WRONG: space before colon, := syntax
q1 --> q2 : x > 0       # WRONG: space before colon

{
  "source_url": "https://...",
  "title": "EIP-7892: Blob Schedule",
  "sub_graphs": [
    {
      "id": "SG-001",
      "name": "get_blob_parameters",
      "mermaid_file": "EIP-7892/SG-001_get_blob_parameters.mmd"
    }
  ]
}

---
title: "get_blob_parameters (EIP-7892: Blob Schedule)"
---
stateDiagram-v2
    direction TB
    [*] --> q_iter: for entry in BLOB_SCHEDULE
    q_iter --> q_return: epoch >= entry.epoch
    q_iter --> q_iter: epoch < entry.epoch
    q_return --> [*]: return entry.params

    note right of q_iter
        INV-001: BLOB_SCHEDULE entries have unique epochs
    end note

function factorial(x):
    y := 1
    while x > 0:
        y := x * y
        x := x - 1
    return y

---
title: "factorial (Factorial Example)"
---
stateDiagram-v2
    direction TB
    [*] --> q1: y = 1
    q1 --> q2: x > 0
    q1 --> [*]: x <= 0
    q2 --> q3: y = x * y
    q3 --> q1: x = x - 1

    note right of q3
        INV-001: y equals x! at loop termination
        INV-002: x >= 0 at every iteration
    end note

{
  "id": "SG-factorial",
  "name": "factorial",
  "mermaid_file": "examples/SG-factorial_factorial.mmd"
}

© NyxFoundation, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/skills/subgraph-extractor of NyxFoundation/speca.

Open the folder on GitHubat commit d173893