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/tercel/spec-forge/tech-design-generationnpx skills add tercel/spec-forge --skill tech-design-generationgit clone --depth 1 https://github.com/tercel/spec-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 | $0.00110 | $0.07721 |
| Opus 5 | $0.00055 | $0.03861 |
| Sonnet 5 | $0.00022 | $0.01544 |
| Haiku 4.5 | $0.00011 | $0.00772 |
Grade A, and why
tech-design-generation 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 — 493 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Tech Design Generation Skill
What Is a Technical Design Document?
A Technical Design Document (TDD) is the engineering blueprint that translates product requirements into a concrete, implementable architecture. It sits between the Software Requirements Specification (SRS) and the actual code, serving as the contract between the engineering team and the rest of the organization about how a system will be built. A well-crafted TDD reduces implementation risk, surfaces architectural trade-offs early, and provides a lasting record of why specific technical decisions were made.
The Google Design Doc tradition emphasizes that design documents are not just about documenting a decision after the fact -- they are a tool for thinking through a problem rigorously before committing to code. The RFC (Request for Comments) tradition adds the dimension of structured peer review, ensuring that designs benefit from collective expertise. Uber and Meta engineering standards contribute a focus on scalability, operational readiness, and production-grade thinking from day one.
This skill combines all three traditions. Every generated Technical Design Document evaluates genuine alternative solutions against explicit criteria wherever a real design decision exists, and documents the rationale behind the chosen approach. The document covers architecture, API design, data modeling, security, performance, observability, and deployment -- everything an engineering team needs to move from design to implementation with confidence.
Seven-Step Workflow
Every Technical Design Document generated by this skill follows a disciplined seven-step process. Each step must be completed before moving to the next.
Sub-agent boundary: Steps 1-3 are performed by the orchestrator (
commands/tech-design.md) in the main context. Steps 4-7 are performed by a generation sub-agent (Task(subagent_type="general-purpose")) that readsreferences/generation-instructions.md,references/template.md, andreferences/checklist.mddirectly. The sub-agent operates in an isolated context and receives a structured prompt with all Step 1-3 outputs.
What ships with it
3 files 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.
- 2d ago First seen · 493 lines · 110 tokens per session scan A fdb04e259474
tech-design-generation is a skill published in the GitHub repository tercel/spec-forge (5 stars, last pushed 1mo ago), licensed MIT. It adds 110 tokens to every session and 7,721 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 2026-08-31.
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