Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/plainlang/plain-forge/add-functional-specnpx skills add plainlang/plain-forge --skill add-functional-specgit clone --depth 1 https://github.com/plainlang/plain-forgeWhat 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 | $0.00111 | $0.01284 |
| Opus 5 | $0.00056 | $0.00642 |
| Sonnet 5 | $0.00022 | $0.00257 |
| Haiku 4.5 | $0.00011 | $0.00128 |
Grade A, and why
add-functional-spec 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 2d 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 — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Add Functional Spec
Always use the skill load-plain-reference to retrieve the ***plain syntax rules — but only if you haven't done so yet.
Workflow
- Identify the target
.plainfile. If ambiguous, ask the user. - Read the entire file to understand existing definitions, implementation reqs, and all current functional specs (including those in
requiresmodules). - Draft the functional spec following the rules below, then run the review pass in
concise-specs.mdover the draft — trim it to the shortest wording that keeps every fact before any other check. - Analyze complexity — use the
analyze-if-func-spec-too-complexskill to verify the drafted spec implies ≤ 200 LOC. If too complex, use thebreak-down-func-specskill to split it, then repeat from step 3 for each resulting spec. - Check for conflicts with every existing functional spec — this is critical. Run
analyze-func-specsonce with the new spec plus all existing specs (in the file and in anyrequireschain) as a single batch. The batched analyzer returns every conflicting pair in one call — do not invoke a pair-by-pair analyzer. For each conflicting pair it reports, runresolve-spec-conflicton that pair; re-runanalyze-func-specsover the touched set after each resolution until the verdict isCOMPATIBLE. - Append the spec to the end of the
***functional specs***section (specs are chronological; new ones go last). - Read the file again to confirm correct placement and syntax.
Rules
Complexity Limit
Each functional spec must imply a maximum of 200 changed lines of code. If the requirement is too large, use the break-down-func-spec skill to split it into multiple smaller, independent specs. Do not include LOC estimates in the spec text.
Chronological Ordering
Specs are rendered incrementally, top to bottom. The renderer has no knowledge of future specs — only previously rendered specs are in context. This means:
- A new spec can reference behavior defined by earlier specs.
- A new spec cannot assume anything about specs that come after it.
- Place the new spec at the correct position if it must come before a future spec; otherwise append at the end.
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.
- 2d ago First seen · 86 lines · 111 tokens per session scan A c4715c7873ea
add-functional-spec is a skill published in the GitHub repository plainlang/plain-forge (55 stars, last pushed 4d ago), licensed MIT. It adds 111 tokens to every session and 1,284 once invoked, about $0.0006 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 2026-08-30.
Other skills, from other repositories
systematic-debugging
Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.
brainstorming
You MUST use this before any creative work - creating features, building components, adding functionality, or modifying behavior. Explores user intent, requirements and design before implementation.
auto-perf-optimize
Run agent-driven VS Code performance or memory investigations. Use when asked to launch Code OSS, automate a VS Code scenario, run the Chat memory smoke runner, capture renderer heap snapshots, take workflow screenshots, compare run summaries, or drive a repeatable scenario before heap-snapshot analysis.
chat-perf
Run chat perf benchmarks and memory leak checks against the local dev build or any published VS Code version. Use when investigating chat rendering regressions, validating perf-sensitive changes to chat UI, or checking for memory leaks in the chat response pipeline.
chat-pet-sprite-creation
Use when creating or changing VS Code chat pet sprite art, sprite sheets, state animations, eye treatments, Stable/Insiders variants, or pet transitions under src/vs/workbench/contrib/chat/browser/widget/media/chatPet.
cpu-profile-analysis
Analyze V8/Chrome CPU profiles (.cpuprofile) and DevTools trace files (Trace-.json). Use when: profiling performance, investigating slow functions, comparing code paths, finding bottlenecks, analyzing timeToRequest, understanding call trees from sampling profiler data, analyzing layout/paint/rendering, investigating…