Instructions and Context
Shape agent behavior with instructions and runtime context.
Instructions describe how the agent should behave. Context provides facts the agent should use while answering.
Instructions
Use .instructions(...) for stable behavior that should apply to every prompt.
const agent = new AgentBuilder("support", model)
.instructions("Answer in a concise, friendly tone.")
.instructions("Ask for missing details before guessing.")
.instructions("Do not invent order status. Use tools when order data is needed.")
.build();Multiple instruction blocks are joined together. Keep each block focused so it is easy to move, remove, or test.
Static Context
Use .context(...) for short facts that should be included with every request.
const agent = new AgentBuilder("support", model)
.instructions("Use the support policy when answering.")
.context("Password reset links expire after 30 minutes.", "password-policy")
.context("Priority support is available for enterprise plans.", "priority-support")
.build();Static context is a poor fit for large or frequently changing knowledge bases. Use retrieval for that.
Dynamic Context
Use .dynamicContext(...) when the relevant facts depend on the prompt.
const agent = new AgentBuilder("support", model)
.instructions("Use retrieved context when it is relevant.")
.dynamicContext(supportDocsIndex, {
topK: 3,
format: (result) => ({
id: result.id,
text: `${result.document.title}\n${result.document.body}`,
}),
})
.build();Anvia searches dynamic context at prompt time and adds matching documents to the completion request.
What Goes Where
| Put it in | When |
|---|---|
| Instructions | It is a behavioral rule |
| Static context | It is short and applies to every prompt |
| Dynamic context | It is searched or changes often |
| Tools | The agent must read or change application state |
| History | It comes from the conversation |
Keep Context Small
Prefer specific context over broad dumps.
const agent = new AgentBuilder("billing", model)
.instructions("Answer only billing questions.")
.context("Invoices are generated on the first day of each month.", "invoice-cycle")
.build();Large context makes answers slower, more expensive, and harder to debug. If a document can be searched, put it behind retrieval instead.