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/sd0xdev/sd0x-harness/feasibility-studynpx skills add sd0xdev/sd0x-harness --skill feasibility-studygit clone --depth 1 https://github.com/sd0xdev/sd0x-harnessWrote 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/sd0xdev/sd0x-harness/feasibility-study)<a href="https://agentmods.dev/skills/sd0xdev/sd0x-harness/feasibility-study"><img src="https://agentmods.dev/badge/skills/sd0xdev/sd0x-harness/feasibility-study.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 | $0.00053 | $0.01783 |
| Opus 5 | $0.00026 | $0.00892 |
| Sonnet 5 | $0.00011 | $0.00357 |
| Haiku 4.5 | $0.00005 | $0.00178 |
Grade A, and why
feasibility-study 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 4d 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 — 181 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Feasibility Study Skill
Supplementary Agent
For each solution option, dispatch background exploration:
Agent({
description: "Explore feasibility of solution option",
subagent_type: "feasibility-analyst",
prompt: Research the feasibility of: <solution description> Evaluate technical feasibility, effort, risk, extensibility, and maintenance cost.
})
Trigger
- Keywords: feasibility, is this possible, can we, should we, explore options, before tech spec
When NOT to Use
- Already have a tech spec (use
/deep-analyze) - Need implementation, not analysis (use
/codex-implement) - Quick question (use
/codex-explainor/codex-architect)
Workflow
Resolve → Decompose → Constraints → Code research → Solutions → Codex discussion → Decision → Report
Phase 0: Resolve the feature context
The sets Phase 1 reads have to come from somewhere, and this skill is invoked directly
(/feasibility-study <topic>) as often as it is invoked from another skill — so it resolves them
itself rather than assuming a caller supplied them:
# The shim over the wrapper. This skill grants `Bash(bash:*)` and no node permission, and the rule
# is that a skill names the entrypoint it is permitted to run — which is also why the shared
# algorithm reference is deliberately not linked from here: it teaches the node entrypoint, and a
# file of commands this skill cannot execute has no business in its reachable graph.
bash scripts/resolve-feature.sh [--feature <key>]
The reply is one JSON document. What this skill reads out of it: scan_error first — the gate
below decides whether anything else in the payload means what it says — then current_authority
(what the system does today) and the design_records entries — design records carry the rationale;
it is the type: requirements subset of them that states what was asked for, which is why
Phase 1 filters before it selects. Each entry is
{ file, type, namespace, confidence, is_canonical, role }, file relative to docs_path. An empty or non-JSON reply is a failure too — node may be
unavailable, which the shim cannot report as a payload. Treat it exactly as scan_error !== false
below.
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.
- 4d ago First seen · 181 lines · 53 tokens per session scan A 9c207de4a0c8
feasibility-study is a skill published in the GitHub repository sd0xdev/sd0x-harness (188 stars, last pushed yesterday), licensed MIT. It adds 53 tokens to every session and 1,783 once invoked, about $0.0003 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.
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building
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diff-driven-docs
Use when a BUILD phase completes, a commit is staged, or a PR is about to be created, and the diff has not yet been reflected in documentation. Also use when the user says "update docs", "sync docs", "document this", or asks whether documentation is up to date.
exploration
Two-mode exploration skill: (1) design dialogue — turn rough ideas into validated designs through collaborative interview before planning; (2) spike — throwaway code answering ONE design question, deleted or absorbed, never shipped. Router invokes mode via dispatch context.
memory-and-handoff
Two-mode skill: (1) session memory — load/persist durable workflow state under .cc10x/ (activeContext, patterns, progress) so context survives compaction; (2) handoff package — portable, secrets-redacted export for a coworker, different tool, or fresh non-cc10x session.
plan-review-gate
Use after saving a non-trivial plan or decision RFC when a fail-closed feasibility, completeness, and alignment review must block execution.