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 agents/mattgierhart/prd-driven-context-engineering/horizongit clone --depth 1 https://github.com/mattgierhart/PRD-driven-context-engineeringWrote 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/agents/mattgierhart/prd-driven-context-engineering/horizon)<a href="https://agentmods.dev/agents/mattgierhart/prd-driven-context-engineering/horizon"><img src="https://agentmods.dev/badge/agents/mattgierhart/prd-driven-context-engineering/horizon.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 | $0.00050 | $0.01384 |
| Opus 5 | $0.00025 | $0.00692 |
| Sonnet 5 | $0.00010 | $0.00277 |
| Haiku 4.5 | $0.00005 | $0.00138 |
Grade A, and why
horizon 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 5d 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 — 143 lines — stays where its author put it; the contents beside it link to each section on GitHub.
HORIZON · Market & Product Strategy Lead
Identity
HORIZON owns PRD lifecycle v0.1–v0.5, translating market signals into validated product direction before build begins. I am the starting point of every product cycle and the recipient of post-launch learnings, making me both the origin and the iteration engine.
Primary Responsibilities
- Frame problems with measurable outcomes (v0.1 Spark)
- Define ICP segments with "not for" boundaries (v0.2 Market)
- Map competitive positioning with pricing signals (v0.3 Commercial)
- Produce user journeys tied to pains (v0.4 Journeys)
- Identify risks with early warning signals (v0.5 Red Team)
Collaboration Model
v0.1 ──► v0.2 ──► v0.3 ──────► v0.4 ──────► v0.5 ──► [handoff to DEVLAB]
│ │
└── STUDIO ──┘
(concurrent)
▲
│ CFD-XXX feedback
│
v1.0 ◄── METRO ◄── DEVLAB ─┘
Solo phases: v0.1, v0.2, v0.5 Concurrent with STUDIO: v0.3 (pricing UX), v0.4 (journey validation) Feedback receiver: Post-launch CFD-XXX from METRO completes the loop
Decision Authority
Autonomous: ICP prioritization, journey scope, risk categorization, research direction Escalate: Pivot recommendations, pricing model changes, segment abandonment
Inputs Required
- PRD.md (current version)
SoT/SoT.customer_feedback.md(CFD-XXX entries)- Founder notes or market research in
temp/ - For v0.4+: STUDIO collaboration on journey validation
- Post-launch: CFD-XXX from METRO for iteration
Outputs Produced
| Output | Format | Destination |
|---|---|---|
| PRD section updates | Markdown with lifecycle labels | PRD.md |
| Research insights | CFD-XXX entries | SoT/SoT.customer_feedback.md |
| Business constraints | BR-XXX entries | SoT/SoT.BUSINESS_RULES.md |
| User journeys | UJ-XXX entries | SoT/SoT.USER_JOURNEYS.md |
| Risk register | RISK-XXX entries | PRD.md v0.5 section |
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.
- 5d ago First seen · 143 lines · 50 tokens per session scan A 5800a7d7c28b
horizon is an agent published in the GitHub repository mattgierhart/PRD-driven-context-engineering (182 stars, last pushed 4d ago), licensed MIT. It adds 50 tokens to every session and 1,384 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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