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/objectstack-ai/objectstack/objectstack-formulanpx skills add objectstack-ai/objectstack --skill objectstack-formulagit clone --depth 1 https://github.com/objectstack-ai/objectstackWhat 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 | $0.06447 |
| Opus 5 | $0.00056 | $0.03223 |
| Sonnet 5 | $0.00022 | $0.01289 |
| Haiku 4.5 | $0.00011 | $0.00645 |
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 yesterday.
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 — 555 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.
Strategic context. The future authors of metadata are AI agents. CEL was chosen because it has (a) a formal grammar, (b) a public training corpus, (c) AST-first persistence, and (d) sandboxed bounded execution. The previous custom Salesforce-flavor engine was deleted in M9.5.
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 Template surfaces).As of 7.6 (ADR-0032) a malformed expression no longer fails silently. It used to evaluate to
null/false(a flow "fired" but did nothing). Nowobjectstack buildfails with a located, corrective, schema-aware message (unknownrecord.<field>→ did-you-mean), and at runtime the engine throws (the flow/rule fails loudly). Thevalidate_expressionagent tool runs the same shared validator so you can check an expression before saving.
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 (schedule.expression is cron dialect) |
| SQL fragment | driver-native; not unified into the expression registry |
Core contract
Every expression in metadata is the same envelope:
What ships with it
1 file 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.
- yesterday First seen · 555 lines · 111 tokens per session scan A 8480b04a81a8
objectstack-formula is a skill published in the GitHub repository objectstack-ai/objectstack (45 stars, last pushed yesterday), licensed Apache-2.0. It adds 111 tokens to every session and 6,447 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.
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