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/activeagents/activeagent/instructionsgit clone --depth 1 https://github.com/activeagents/activeagentWhat 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 | $0.00025 | $0.02519 |
| Opus 5 | $0.00013 | $0.01260 |
| Sonnet 5 | $0.00005 | $0.00504 |
| Haiku 4.5 | $0.00003 | $0.00252 |
Grade A, and why
instructions 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 2d 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 — 367 lines — stays where its author put it; the contents beside it link to each section on GitHub.
{{ $frontmatter.title }}
Instructions are system-level messages that guide how agents behave and respond. They define the agent's personality, capabilities, constraints, and how it should use available tools. Think of instructions as the agent's "operating manual" that shapes every interaction.
Why Instructions Matter
Well-crafted instructions help agents:
- Understand their role and capabilities
- Know when and how to use available tools
- Maintain consistent behavior across interactions
- Handle edge cases and error scenarios appropriately
- Provide responses in the desired tone and format
Setting Instructions
ActiveAgent provides five flexible ways to define instructions, from simple strings to dynamic ERB templates.
1. Default Instructions Template
The simplest approach: create an instructions.md (or instructions.text) file in your agent's view directory. ActiveAgent automatically loads it when you call prompt without explicit instructions.
::: code-group <<< @/../test/docs/agents/instructions_examples_test.rb#default_template {ruby:line-numbers} [agent.rb]
<<< @/../test/dummy/app/views/docs/agents/instructions/default_template/agent/instructions.md.erb{erb:line-numbers} [instructions.md] :::
Strict Loading: Pass instructions: true to enforce strict template loading. This will raise an error if the template file cannot be found, useful for catching missing instruction files in production.
# Raises error if instructions.md is missing
generate_with instructions: true
When to use: Most production agents. Keeps instructions organized, version-controlled, and easy to iterate.
2. Inline String Instructions
Pass a string directly to generate_with for simple, static instructions:
<<< @/../test/docs/agents/instructions_examples_test.rb#inline_string {ruby:line-numbers} [agent.rb]
When to use: Quick prototypes, simple agents with minimal instructions, or when instructions fit in one clear sentence.
3. Custom Instructions Template
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.
- 2d ago First seen · 367 lines · 25 tokens per session scan A 51b02e893f96
instructions is an agent published in the GitHub repository activeagents/activeagent (971 stars, last pushed 6d ago), licensed MIT. It adds 25 tokens to every session and 2,519 once invoked, about $0.0001 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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