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 skills add objectstack-ai/objectstack --skill objectstack-formulagit clone --depth 1 https://github.com/objectstack-ai/objectstackWrote 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/objectstack-ai/objectstack/objectstack-formula)<a href="https://agentmods.dev/skills/objectstack-ai/objectstack/objectstack-formula"><img src="https://agentmods.dev/badge/skills/objectstack-ai/objectstack/objectstack-formula/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/objectstack-ai/objectstack/objectstack-formula"><img src="https://agentmods.dev/badge/skills/objectstack-ai/objectstack/objectstack-formula.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00131 | $0.05852 |
| Opus 5.5 | $0.00052 | $0.02341 |
| Sonnet 5.5 | $0.00026 | $0.01170 |
| Haiku 4.5 | $0.00013 | $0.00585 |
Grade A, and why
objectstack-formula 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 today.
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 — 463 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Expressions (CEL) — ObjectStack Formula Protocol
ObjectStack has one expression language across every domain that needs computation or boolean predicates: CEL (Google Common Expression Language). This skill is the canonical reference for AI authors emitting formula / condition / predicate / dynamic-seed metadata.
Predicates / formulas are bare CEL — never wrap field references in
{…}braces. The #1 authoring mistake is a condition like{record.rating} >= 4: in CEL,{…}is a map literal, so it is a parse error. Write bare CEL:record.rating >= 4. Braces are only for{{ … }}text templates (see Cron and template surfaces).
Skill Boundaries
| Need | Use instead |
|---|---|
Define a type: 'formula' field |
objectstack-data (and embed CEL via F\...``) |
| Define seed records | objectstack-data (use cel\...`` for dynamic dates) |
| Author flow / automation step | objectstack-automation (use P\...`forcondition`) |
| Author L2 hook body (TS code) | objectstack-data |
| Cron schedule | objectstack-automation |
| SQL fragment | driver-native; not unified into the expression registry |
Core contract
Every expression in metadata is the same envelope — dialect plus source,
with optional ast and meta — declared as Expression / ExpressionInput in
shared/expression.zod.ts. Three registered dialects:
| Dialect | Engine | Purpose | Helper | Example |
|---|---|---|---|---|
cel |
@marcbachmann/cel-js |
Computed values + boolean predicates | cel`...` / F`...` / P`...` |
cel`record.amount * 1.1` |
cron |
built-in validator | Recurring schedules | cron`...` |
cron`0 6 * * MON` |
template |
built-in interpolator | {{path}} text interpolation (notif/prompt/title) |
tmpl`...` |
tmpl`Hello {{record.first_name}}` |
What ships with it
2 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.
- today Changed 363618ff708f
- 2d ago Changed 76d52da423fe
- 3d ago Changed bd0e35fd51c9
- 5d ago Changed ffd331456fd3
- 8d ago Changed · +1 lines 9a20a3169e86
- 1mo ago Changed · +7 lines f2998d2c055a
- 1mo ago Changed 8553cbf27ee1
- 1mo ago Changed · +5 lines 1ee9ddd7d56e
- 1mo ago Changed · -105 lines · +20 tokens per session ac5ab8d8c1f5
- 1mo ago First seen · 555 lines · 111 tokens per session scan A 8480b04a81a8
objectstack-formula is a skill published in the GitHub repository objectstack-ai/objectstack (72 stars, last pushed today), licensed Apache-2.0. It adds 131 tokens to every session and 5,852 once invoked, about $0.0005 per session on Opus 5.5. 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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