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 charlieviettq/awesome-agent-skill --skill agent-tool-contractsgit clone --depth 1 https://github.com/charlieviettq/awesome-agent-skillWrote 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/charlieviettq/awesome-agent-skill/agent-tool-contracts)<a href="https://agentmods.dev/skills/charlieviettq/awesome-agent-skill/agent-tool-contracts"><img src="https://agentmods.dev/badge/skills/charlieviettq/awesome-agent-skill/agent-tool-contracts/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/charlieviettq/awesome-agent-skill/agent-tool-contracts"><img src="https://agentmods.dev/badge/skills/charlieviettq/awesome-agent-skill/agent-tool-contracts.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00046 | $0.00389 |
| Opus 5 | $0.00023 | $0.00195 |
| Sonnet 5 | $0.00009 | $0.00078 |
| Haiku 4.5 | $0.00005 | $0.00039 |
Grade A, and why
agent-tool-contracts 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 11d 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.
What it actually says
Agent tool contracts
Tool design rules
- Verb-noun names —
search_issues,create_draft_pr(notdoStuff). - Minimal parameters — fewer required fields; sensible defaults in description.
- Explicit side effects — "Creates...", "Deletes...", "Read-only" in description.
- Bounded output — paginate or truncate; return summary + pointer for large data.
- Stable errors —
{ "code": "NOT_FOUND", "message": "..." }.
Schema quality
- Types and enums for categorical fields.
- Examples in parameter descriptions.
- Reject unknown enums at validation layer.
Idempotency and safety
| Operation | Pattern |
|---|---|
| Read | Safe to retry |
| Create | Idempotency key or dedupe by natural key |
| Update | Version or ETag when concurrent edits possible |
| Delete | Soft delete or two-step confirm in description |
AI-native CLI (when applicable)
--jsonfor machine output; stable field names.- Exit codes: 0 success, non-zero with stderr message.
--dry-runfor mutating commands.
Review checklist
- Description tells the model when NOT to use the tool
- Errors actionable (what to fix, not internal codes only)
- No overlapping tools with ambiguous choice
- Integration test with representative agent prompts
Related
mcp-builder for MCP-specific packaging; agent-evaluation for measuring tool accuracy.
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.
- 11d ago First seen · 48 lines · 46 tokens per session scan A b18e4542b4fc
agent-tool-contracts is a skill published in the GitHub repository charlieviettq/awesome-agent-skill (25 stars, last pushed 1mo ago), licensed MIT. It adds 46 tokens to every session and 389 once invoked, about $0.0002 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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