Borrowing it
Nothing to install: this file belongs to georgeturneruk/tckit. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/georgeturneruk/tckit/main/.claude/skills/tc-write-st/SKILL.mdgit clone --depth 1 https://github.com/georgeturneruk/tckitWrote 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/skills/georgeturneruk/tckit/tc-write-st)<a href="https://agentmods.dev/skills/georgeturneruk/tckit/tc-write-st"><img src="https://agentmods.dev/badge/skills/georgeturneruk/tckit/tc-write-st.svg" alt="Measured on agentmods" 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 | $0.00270 | $0.03071 |
| Opus 5 | $0.00135 | $0.01536 |
| Sonnet 5 | $0.00054 | $0.00614 |
| Haiku 4.5 | $0.00027 | $0.00307 |
Grade A, and why
tc-write-st 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 8d 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 — 87 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing ST through TcKit
Follow this procedure every time you produce ST that will be written to the project.
Tool selection — read this before calling anything
These TcKit writer tools go through the selected writer backend (the XAE Automation Interface by default on Windows; a deterministic on-disk XML writer elsewhere or when TCKIT_WRITER=xml), which keeps GUIDs and project cross-references consistent. Use them in place of Edit/Write on .TcPOU or .plcproj files.
| Request | Tool |
|---|---|
| Tweak one line in a method / action / property body | UpdateMethodBodyPatch(pou, method, old, new) |
Tweak one line in the POU's own declaration block (FB-level VAR) |
UpdatePouDeclarationPatch(pou, old, new) |
| Tweak one line in the POU's own cyclic body (FB / PRG implementation) | UpdatePouImplementationPatch(pou, old, new) |
Add one variable to a VAR_INPUT / VAR_OUTPUT / VAR etc. scope |
AddVariable(pou, scope, declaration, item?) |
| Rewrite a method / action / property body | UpdateMethodBody(pou, method, code) |
| Rewrite the POU's own declaration block | UpdatePouDeclaration(pou, code) |
| Rewrite the POU's own cyclic body (FB / PRG implementation) | UpdatePouImplementation(pou, code) |
| Add a brand-new method to an existing POU | AddMethod(pou, method_name, code) |
| Add a brand-new property to an existing POU (Get, Set, or both) | AddProperty(pou, name, return_type, getter_code?, setter_code?) |
| Add a brand-new POU (FB / function / program / interface) | AddPou(name, pou_type, code) |
Add a brand-new GVL (VAR_GLOBAL declarations) |
AddGvl(name, code) |
| Add a brand-new DUT (struct, enum, or union) | `AddDut(name, code, dut_kind="struct" |
| Create a brand-new PLC project | CreateProject(name, path) |
| Open / re-open a TwinCAT solution in XAE | OpenProject(solution_path) |
| Read the current item body before deciding on a patch anchor | GetPouItem(pou, item) (reader) |
Read just the FB-level VAR block before AddVariable |
GetPouDeclaration(pou) (reader) |
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 8d ago First seen · 87 lines · 270 tokens per session scan A 60c585c40ca1
tc-write-st is a skill published in the GitHub repository georgeturneruk/tckit (5 stars, last pushed 14d ago), licensed MIT. It adds 270 tokens to every session and 3,071 once invoked, about $0.0014 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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